Okay here is my situation.  I recently picked up a nice Dave lauck worked upper. It was one of his Perimeter defence carbines.   Anyway, the upper receiver bugs the crap outta me.  its nicked up all over and on the back end its so bad that the charging handle is getting all nicked and scratched up.  Not to mention everytime I grab the charging handle my fingers are getting cut.  In short, i need a new upper.  the lower is a Larue stealth, the hand guard is the badger rail system.  I plan  on using the PRs stock with full length buffer.  
so first which upper,
i am leaning towards MUIR from vltor or more than likely the stealth upper from good ole larue.  how difficult will it be for me to change or should I sent it a gunsmith.  advice
thanks
sam

It's not too hard to change an upper, but you'll need a few special tools (barrel wrench and upper reciever block).  The tools would cost around $60, which is porbably only a little less than what a gunsmith would charge.  If you can locate someone who has the tools and has done it before its a no brainer and can be done in about a half hour.  Check in your home town forum for help nearby.

All you really need is a barrel wrench. A reciever block is nice but you don't really need it. (with a flat top upper, A1/A2 uppers you need the block)



Just place the upper in a vice sideways (so that the rail is facing one jaw and the bottom of the upper is facing the other) then place a piece of wood on either side as a buffer between the reciever and the jaws of the vice. Works great and no fancy tools required.

Ask someone in your hometown forum if you can borrow tools

I prefer to hold the barrel in place with wooden blocks. The aluminum receiver could flex under pressure if you end up going to 80ftlbs.

Thankfully I've never had to go near 80ft lbs, but I believe the original design was to hold the barrel in place and attach the upper to it. Did you modify the wood blocks before you clamped them around the barrel? I might want to try this on my next build