gimme some tips

ok let me start off by saying that i need some help and information. ok, first of all i might be gettin a 90' civic 4dr for free. im not sure how many miles is on it but i know its quite a bit. There is some rust by the back door probably as big as the length of ur elbow to ur fingertips, about how much would it cost to get that fixed. next i dont see any nice body kits for the 4dr, can a bumper from a hatchback fit onto the sedan. next im almost positive i would throw some kyb agx shocks onto it, but im not sure about what coilovers. Do u think skunk2 or groundcontrol would be better.

KYB AGX - does not recommend using them with cheesy coilover springs & will void any & all warranties.

is the rust on the door? if it is just get a new one and get it painted or something.....probably be easier than fixing the existing rust