Want to fix a hole from rust
 

1997 Plymouth Grand Voyager SE 3.3 passanger side past the sliding door to the tire there is a small area below the trim. I have a hole there and would like to repair it. Is there an inexpensive way to do it. I read if you want to start repairing rust its better to buy a car with no rust.

I was thinking I could somehow cut out the section under the trim and splice in a new piece and keep the car going with out a big rust hole.
I have swapped a sliding rusted door with a hole from rust same color already from the junk yard. It wasn't to bad but I can't clearly see how to fix this with in my capabilities.

My best guess was I could get a piece from another car and attach it somehow, however its not like you can just pull it by removing the bolts.

Its welded in and I'm not sure what it would cost to get it welded in if I even could cut it out from another car?

Is there a best way to do this for a novice DIY hobbiest.