Few Repair/Maintance questions for new RV owner

Ok, i will try the tire thing and see if out of round.
What kind of insulation did you use in the dog house to quiet it down.
If i replace the headers do i have to replace the whole exhaust system or are they bolt on? The exhaust is in good shape all the way back so hate to replace it all.
Can i just replace the AC compressor my self and add freon from parts store, or do i need to replace compressor and take it somewhere for them to fill it?