==> https://drive.google.com/open?id=1ErvI2CB8UUhBa_-L1dVRnI_3jPoX93rF <== above is simple system example of save 'n load system (saves to text in your computer). it's pretty simple when near ...

Make sure that your sensor (whoever clicks)is set to tap mode

(blend example file) ==>https://drive.google.com/open?id=1yny39dZCLL8pv886YI0fmaarocPItcwh<== in this example you can drift(go sideways) get drift score(depending on drift speed) very simple ...

" I basically just want to be able to run my car into another object and have it randomly deform." that is very easy to do . add collision sensor(senses collisions) to your car and add edit object ...

Select 370z and hit ctrl+a and aplly scale and do this for its wheels , set wheels to no collision(physics tab). Also set Camera 2 camera object to 370z(logic actuator) if you are making split screen ...

add property to the door which tells when the door is locked or unlocked . then add trigger which sends message "unlockdoor" (and unlocks the door(sets locked to 0)) . then add animation

Add empty(which is parented to character bone for example arm) which spawns the shield. and then add logic bricks that parents the shield to the character