you need to tighten the brass housing if you're talking about the throttle linkage moving. if you're talking about the needle adjusting itself you'll need to replace the oring in there.

spare rims - proline velocity dish for 1/10 trucks, they also have a good range of tires, find what suits you best.

any standard fuel line will be fine

the OS air filters are good you want the 102 one. it doesn't matter which way it faces as long as it is on, never run it with it off.

run your engine in rich, search on "running in" and you should find several posts i have posted about running engines in.

pro line xxxnt bodies will fit, you can make most 1/10 truck bodies fit, you just need patience.

the lower % nitro the longer your engine will last, don't go above 20%. i personally run 16%.

if you are running the stock tank, run a fuel filter, the dubro ones are good.