this is my first post here, hey everybody
anyways, to the point.
the first thing you've got do here is get a jack and some STANDS. do not ever ever ever under any condition work under a car not supported by jack stands, unless you want to die. they are cheep... you can get them for under $10 each, check out sears, walmart, auto parts store, or i got some good ones from target 'cuz i worked there at the time. as far as a jack goes, you can spend $100 or so on a nice alumnium one, but theres really no reason. you can get a cheepie for ~30 at just about anywhere that you can get the jack stands at. no, its not going to be the best or have the highest weight capacity, but most all floor jacks are 3000+ lb rated, which is more than you're ever going to need for a car. stay away from bottle jacks, they're great for keeping in your car/truck in case of an emergency, because they're small and can cary a lot of weigh, but they are a real pain to work with since they don't have wheels, and have a very small footprint.
ok, great, you've got yourself setup with a good jack and some stands. now, where do you pick the car up? well theres a good chance that the "jacking points" in the front, basicly the spot thats in the corner of the rocker panel and the back of the wheel well, have long since rusted out. that means you cant put any load there. i generaly will pickup the car under the rocker panel, asuming that theres enough of it there to suppor the weight of the car, and than put the jack stand under one of the suspension mouning points... thats just prefrence though, i'm sure others will have their oppinions, just use your better judgement. before you climb under the car, wiggle it around a bit with your hand to make sure that its supported well and isn't going to topple over ontop of you if you start pulling hard on a rusty bolt or something
ok, so finaly we get to the original question... rust repair. well i'm knee deep in restoring a 65 mustang, so i know a thing or two about rust repair. it is no fun. period. depending on the severity of the problem spot and the degree of "restoration" you plan to do, theres different options. you're going to want to aquire some tools, aproximatly in this order: an asortment of sand paper, wire brush for your drill, dremel tool, angle grinder. if your rust spots are just paint chips that have rusted, you can proly just sand away the rust with some sand paper, prime it, sand the primer, paint the primer, and be good. if they are more serious rust spots where the metal has started to pit, you will need to get a wire brush of some sort to clean the rust out of the pits... sand paper won't do it. they sell atachments for power drills that do a so-so job, you can get attachments for a dremel that will do a pretty good job, but take forever, or you can splurge and get yoruself an angle grinder with a wire wheel that will do an amazing job. something you have to keep in mind, if you do not get every tiny little microscopic spec of rust off of the surface of the meal, and get it down to bare, shiney, clean metal the rust WILL come back. you have to get the meal shiny, if it turns a dark black/gunmetal color the rust is NOT gone yet. another thing, if you are using some sort of power grinder/wire wheel on metal, the metal will get hot. this is bad, since the metal will expand and warp perminantly. it is VERY hard to fix... ask me how i know. thats pretty hard to do with anything but the angle grinder, however. just be carefull you do not sit in one spot for a long time grinding away at the rust. take frequent breaks to let the metal cool and you will be ok.
if the metal is severly pitted, which theres a good chance it is if you're talking about door or trunk, etc, rust, than you can get some spot putty to fill in the pits. you can use bondo as well (or one of the knock off's) but it is more difficult to work with, imo, for such a small job. again, someone else's oppinion might differ here... this is just my experience. once you get everything cleaned up, filled in, and sanded down smooth you can paint it with that spray can touch up paint avalible at the auto parts store. the color usualy matches very well, but you will get pretty bad orange peal out of a spray can, and theres not much you can do about that other than sand it out. either way, it looks better than rust.
as far as your exaust system... i woudln't worry too much about it. there is not that much that can stand up to the temperatures of an exaust system, even header paint (similar to bbq paint...) will burn off. most exaust systems are alumnised, which prevents them from rusting pretty well. any exaust shop should be able to built you a new cat-back exaust system for well under $200. its not going to be a race ready performance exaust, but it will get the job done just fine and will be WAY less money.
well i hope i've been able to help some people out here... good luck w/ your car.