g26er - I don't know what pistons and oil come in the RTR. If you want to try the race roller setup, it's probably a good idea to just rebuild everything anyway. I'm pretty sure you gotta change the diff oil and other things as well.
I think that's how the swaybar sets work, it should be the same.
kmaheartless - The chassis will last quite a while. When the rear of the chassis is worn so thin that you could shave with the edge, that's when you should replace it...haha.
Actually, it might be a good idea to do it sooner than that, or you will wear out the pivot blocks too.
When the driveshaft joints get sloppy and the pins are worn out, it's a good idea to replace them. You can replace just the pins and get some more life out of the shafts.
I'm not a fan of cleaning these cars with water. If you're pulling the car apart into pieces, you can rinse stuff off in the sink but make sure you're not getting hinge pins, bearings, etc. wet and then not drying them off completely! For at-the-track cleaning, I suggest using WD-40 and an old toothbrush.