Literally everything but wheel builds as one of my LBS' (little independent one near the Kursaal, none of this Evans/ Cycles UK shit) does the most incredible builds cheap for me. 2 sets of stock wheels and my old 24" set, never had the slightest problem - front even stayed fairly true when i put my foot through it going down pier hill at 20mph
Taught myself how to do the majority of things, but having superstarengineerdad™ on hand has helped a fair bit - if i couldn't do something when i was younger he'd show me how to do it and from then on i've done it myself. Think that's the best way, it pains me to see kids on here who go to their lbs for literally anything - how do they ever expect to fix something if they're out on a ride or just somewhere a long way from home? Bag full of tools, some cable ties, few spares and i'll sort 99% of problems one way or another.