For the 454SS engine, its $335.23 for the Gibson Exhaust System.

It's not that hard to do.  The trickiest part will be ensuring you get the exact pipe you need.  If you go to a lower end parts store (Autozone, Pep Boys, etc...) you will either not find it or get the wrong one.  Stores like that do not deal with exhaust well.  If you go to a Carquest or a Napa, more than likely, you will get the exact pipe you need, but depending on the pipe, you may have to pay a bit.  Since that is a common truck, I wouldn't think so.  I have been selling auto parts for quite a few years now and this is my thing, so trust me on this. 

I don't know for sure what your exhaust looks like, but if I remember correctly, the muffler is in front of the rear axle and the tail pipe runs over that and out the back.  If it does, then you can expect to pay $50 to $100 for the part.  If the muffler is behind the axle and the tailpipe is less than a foot long, then it'll be less than $20.  I'll check tomorrow at work and see what I can find.  Either way, installing the new piece is not hard.

If you choose to repair the piece, just go to any parts store and ask them for 'muffler bandage.'  It's made by a company called Permatex and most places have it.  Just wrap it around the hole, let it dry, and off you go...

Take my advice, and just learn how to do it right, instead of trying to patch it.  In the long run, it'll pay off.

Kevin