Once you've got a servo that is strong enough to turn the wheels properly and you've checked your servo saver, just keep driving! Practice, practice, practice!
Keep you eyes on the for sale section when decide you want new batts, motor, speedo etc. you can get some good bargains!
Don't be afraid to come on here and ask detailed questions; the more info you can provide the easier and quicker it'll be answered.
Let us know how you get on in the future