Bpittin- If you bought the car used, it would be a good idea to go through the diffs and shocks and change out all the o-rings, just as a precaution. Also, since you'll be rebuilding the car, it's a good idea to loctite everything down. There's different opinions on what to loctite, but I use blue loctite on just about every screw, cause t doesn't hurt and can only help. Check the pins and cvd's to make sure they are in good order, and clean and grease the drive shafts while you're at it.

As far as electronics, good luck on a consensus. 4s is popular because that is ROAR approved. Look for something with at least a 35c rating or above, soft case lipo's aren't ROAR approved, but it just matters what your track says about softcase and whether or not you want to run hard or soft cased batteries. There's no performance difference, just safety differences.

All 8th scale ESC's have people saying good and bad things about them. The mamba speed control is stout, but sensorless, which I personally don't like. The Tekin RX8 is sensored, which makes it smoother and they have very good customer service. Their updated RX8's seem to be more durable too. For a motor, the Tekin 1700 or 1900 would probably be best for that track. It's not a big track and anything larger than those motors would just make the car harder to drive, imho. And pinion will depend on motor. When you decide on the motor to run, then you can look into gearing. Search "gearing" on the "Search this thread" option at the top of the screen, should help you get opinions on where to start and motor temps to look for.

Servos..... welll I run an Associated DS1015, but you'll get many opinions on that too. I would try to find a servo with around 150-200 oz/in. of torque.

There's no right answer, there's a lot to a racer's preference. A good idea is to head down to the track and try to scope out some of the 8th scale guys' cars and see what's working for them. Kind of a long reply, but that was a loaded question. Good luck.