Savage 21, new guy!!
Dont be fooled by the plastic shocks, they work very well and like i said plastic is best for bashing (flexible, light, strong and cheap). However one of my shock is defective from the factor (sticks at full extension) and teh adjustable preloads suck on the plastic shock. It adjustable preload is important to you then go for metal shocks with threaded preload settings.
my comments re: the servo would be the same as thoses above. u can keep the stock one, just dont hit anything solid with the front end or u will strip out the plastic gears. Metal gears was the most important characteristic i shopped for, with torque being second. If you dont race, i dont think the servo speed is that important.