Welcome to the Bike Forums.
That old bike, unless it has great sentimental value to you, is not worth the upgrades that you have suggested. Please do not take that as an insult. The Raleigh is a good enough bike to clean up and ride, but to spend all the money to implement the upgrades you seek will prove to be not cost effective.
Just to get this one road worthy and looking good has set me back close to $250.00 already and I have not purchased tires, or cables, or brake blocks yet. There goes another hundred dollars, or close to it. To that add that I do all of my own work. By the time I get this done, my cost will be between $350 and $400. And I did not have to change brake calipers or the transmission or anything else. Anyway, this was free to me...
and it looks like this now, brush on paint job and all...
The point is that, by the time you alter the frame to accept disc brakes, and buy a front fork that accepts disc brakes (probably screw up the geometry of the bike), and disc brake wheels, and just the few other items you mention, will set you back hundreds of dollars, unless you find a decent doner bike. Plus, who will do the work? For what you want done, the labor costs will be high, in my opinion.
Anyway, your bike, do what you feel best but, were I the you, I would seriously consider finding another bike as my starting point.