First welcome to the forum.

Every time I race I get mine nasty but clean and service it after each day of running. Even if all I do is bash I clean it. VERY important to keep the air filter clean and oiled!

DO YOU HAVE A MANUAL? If not you can go to HPI web site and down load it for free.

You should only run silicone shock oil in the shocks and you fill it from unscrewing the top. For bashing I recommended 30-weight shock oil and no more then 40. You need to check the manual out on how to bleed the shocks.

For bashing I would think the stock springs would be fine.

I think these little vehicles are very easy to work on but do not know your ability so it hard for me to say how easy it will be for you but I recommend you go for it. This is how you learn.

Most of the time when I replace tires I replace the wheels, as most of the time when my tires are shot my wheels are all beat up but here is a link on how to get the tires off.
http://misbehavin-rc.com/pit-lane/bo...ling-tires.asp

As far as tires being I do only run off road I do not know what to recommend for both off and on road. Most people that run both have to sets of tires one for each.

If you do not want to spend much money then I would not get any carbon fiber parts. Sorry but this is not a cheap hobby.
Have other question ask.