Project Bike Advice/Tips Needed

Hey everyone! I've been working on my first bike ever, a 1991 Specialized Rockhopper Sport. I've never built or worked on a bike before, but I've got done some of the super basic stuff: handlebars, pedals, cantilever brakes + pads, tires + tubes, installing a storage rack, etc. The primary goal of this bike is LEARNING... some of these pairings might not be ideal, but I'm trying to LEARN how things work and how to do it.

That being said, I'm about to take on a biggie: the handlebar/brake lever/shift lever/derailure upgrade. Going from from stock to:

• 70mm rise handlebars
• Shimano M315 shift levers (front 3, back 7)
• Dia Compe SS6 brake levers
• Shimano RDTX800 Rear derailleur
• Shimano FDTX800-(I did the 3, to match my post angle)
• Basic shift/brake wire kit from Amazon that included the cutting tool

I think that's about it? I'm armed with patience, common sense and Youtube (I'm looking at you, Park Tools... the best learning resource I've found!)... any other suggestions, tips, tricks, "wish I would have's" or "watch out for..." type info I should know before I enter the void?