Simple rust/autobody shop question

Hello, let me start of by introducing myself, my name is Scott. I pretty much have no automotive experience other than simple oil changes and tune-ups, however I plan on working on an almost destroyed 89 Camaro and to gain a bit of knowledge, so starting in the spring you should see more of me. But thats not the question right now anyways. I currently drive a '83 El Camino (I know wrong section still has a year before it's a classic) and about a year and a half ago it had no rust. Now there is a hole below the gas, and it's bubbling on the other end. Also on the bottom of the bumpers are starting to rust. The car still has its stock paint and I knew the previous owner, the only owner, and know he didn't through a cheap paint over rust before he sold it to me. So my question is how much should this cost to get a decent job to remove the rust and paint the particular areas? I've also heard that preping parts will reduce repair costs, how significantly? Correct me if I'm wrong but it shouldn't be to difficult even for a first timer to remove some rear trimming and sand the rust away to metal correct? Also is there any other simple things I could do to reduce costs? Any additional advice you could offer would be appreciated help.

One thing you can do to prevent further damage in the interim is to apply an encapsulating rust converter to stop additional rusting, and to firm up the already rusted areas.

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Even if some portions of the panels will need to be replaced, minimizing the spread of rust may be beneficial. When it comes time to do the repair and refinishing work, removing all the trims, emblems, bright work, moldings, marker lamps, inner fenders, and anything else which is not part of the affected sheet metal should reduce the time and labor costs for the repairs.