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.