If you have a plumber who happens to have one of these .. .. ..

http://www.msvalves.com/sting.html

he can solder onto short stubs without anything more than a slight
discoloration of adjacent drywall or other painted surfaces

Without question they will need to cut in to the drywall. 3/4" comming
out of the wall is no where close to what is needed. They have no way to
solder on the new fittings. They also need to be concerned with the paper
backing on the drywall catching fire when they are soldering. What may look
easy to you "could" be a lot more involved.
350, while it might sound steep is, at least around here (Boston), a
reasonable amount for a licensed plumber onsite. Rates here are 90-125+ per
hour. 50$ stock, 2-3hrs onsite, your right there.