RE: steering servo
Does your transmitter have dual-rate? on mine it's a thin wheel recessed underneath the transmitter steering wheel. I didn't even know it was there for like weeks. At one extreme you'll have maximum steering throw (for low-speed tracks) and at the other it decreases the throw for high-speed tracks so you don't over-turn and spin out. You might have bumped it toward the latter.
If it's not the dual-rate, remove the horn off the servo and see if the servo operates fine with no load on it. Then grab the little white splined bit on the servo and see if it'll still operate, even with your fingers resisting the turn. If it does, then your servo is fine, but instead either the horn is on too tight (so it rubs against the servo case) or some part of the steering mechanism is binding or stuck. I guess you could probably work that out by just grabbing the front wheels and 'steering' them (with the receiver turned off!).