My main commuter is going down for major service, and I'm looking at changing quite a few things... I want to add a dynamo hub/lights (easy from what I understand) and I'd like to change from an 8spd derailleur setup to an 8 or 11spd alfine hub. Is there a good way to do this or am I chasing an idiots dream?

Whether or not it is a good thing to do is completely up to you.

A good way to do it will depend on the kind of rear dropouts on your bike. If they are vertical -- the wheel drops down out of the bike -- they you will most likely need a tensioner of some kind to pick up any chain slack. There are a number of different kinds around and if you are exceptionally cheap, you could even use the existing derailleur as a tensioner. If you have a horizontal or near horizontal dropout -- single speed/fixed gear or older geared bike style -- you don't even need a tensioner.

Cabling back to the IGH hub can be tricky as well, depending on how the cable is routed and what hard frame stops came stock on the bike. But not insurmountable.

You do realize that both of your "upgrades" require new wheels.... right? Or at least your old rims re-laced to new hubs (the dynamo and IGH) with new spokes. At that point you may as well replace the rim and have an extra set of wheels.

It's not a hard process really. Typical bike upgrade type of things. You may need to buy a problem solver's cable stop for your chainstay for the shifting mechanism on the nexus/alfine. Often many bikes' rear cable stop is too close to the mechanism requiring very sharp bends in the housing to be used. (Despite this, I still used the one on my cross check.)

If you aren't going with disk brakes, buy the nexus red band, it's identical to the alfine (at least in the 8 speed variety) except it doesn't support a disk brake. (And it's cheaper.) I personally have the nexus with a rollerbrake. It's another weather proof brake that's also silent forever. (Unlike disk brakes.) It doesn't have the stopping power of a disk brake, but it's great for a commuter. I went through a roller coaster with mine. At first it was good, then I hated it for a while, now I like it again. I think the hate came from the fact that I cabled it using only partial housing with exposed cable. That made the feel of the brake awful. Once I switched over to full housing it made the brake so much better.

Remember, the nexus/alfine require special shifters. No other shifter will work with them.

From what I've heard, the 8 speed nexus/alfine hubs are more bulletproof than the 11 speed versions. When I was doing research, I found that the 11 speeds liked to slip and leak, so I went with an 8 speed. Plenty of range. I mainly stay in 3-6 gears. 7-8 on the downhills or with a tailwind. I'm never in 1. 2 uphill into a headwind or if I'm towing. 5 is the "direct drive" gear, which is the most efficient, so I aimed to have that be my most used gear. I used the smaller of the two cogs they give you. Mine has been good for ~4 years and many thousands of miles now. My dynamo requires less care and has worked equally long. (Best purchase I ever made for my commuter.)

Also be aware, dynamo lights are expensive as hell in the US. (Much cheaper overseas.)

Also, as mentioned above, you'll need a tensioner (you can use your derailleur) if you have vertical dropouts.

It's actually pretty simple if you have a frame with horizontal dropouts and 132mm or 135mm spacing. You can respace the frame if it's from the 80s.

You can use the Alfine 8 without disk brakes, it has a rubber cover for the disk connector.

The Alfine 8 is only 134,37 € https://www.bike24.com/1.php?content...7C%7C%7C%7C%7C
You also need the Small parts package: https://www.bike24.com/1.php?content...7C%7C%7C%7C%7C
The rear sprocket https://www.bike24.com/1.php?content...7C%7C%7C%7C%7C

And a shifter of your choice: the Shimano trigger https://www.bike24.com/1.php?content...0,2,116;page=3
or the MicroShift bar-end (it'll require a cable adjuster) https://www.niagaracycle.com/categor...-nexus-inter-8

Then you have to get new spokes and relace the wheel.

I assume you are contemplating converting your Trek District 8 and there are challenges but nothing that can't be overcome. Most others have discussed what will be needed and the costs associated with the conversion. I wonder if it is financially more fiscal to sell what you have and purchase a Trek Lync 5. It has everything but the dynamo but does have the USB charged lights. With the Lync you also get the carbon belt drive which you may or may not like. Your conversion would be cheaper but having a nice new shiny bike may outweigh that.

Read data, overlock nut distance.. may be 135.. (my Sram i9 is, so is the Rohloff)

Sturmey Archer makes a variety of hubs with a variety of speeds and widths ... do you homeswork

have a vertical dropout frame? chain tension ers take up the slack..
longer horizontal dropouts? you dont need it..

I honestly was considering the alfine 8 due to the bulletproof nature of it. I'm planning on re - lacing the wheels with the new hubs, whether I go IGH or to a 10spd derailleur setup (to convert the rear to centerlock rotors, the dynamo is centerlock and it would bother me to no end of the brakes didn't match (though I plan on using a 140mm rotor out back instead of the 160mm it currently has) the bike has vertical dropouts, so I guess I'd be picking up a tensioner. I don't want to pick up a new bike, this thing has sentimental value to me, and the fact it's a tad beat up at this point in its life just adds to that value to me. It's been a wonderful commuter

Need to figure out the light situation though, been eyeballing Busch and Mueller lights

OK, but so many people have an allergy to doing measurements, here..