Easy to do and very common. As the other post said, you may have to readjust the front derailleur--if it's set up properly now, there may not be enough clearance for a larger ring. You might have to install a longer chain, too (there's probably enough slack in the old one, taken up by the rear derailleur, but it's a possibility). Any bike repair book can tell you how to do it, or check www.parktool.com.
A gain of one to three teeth, from 49 to 50 or 52, isn't a lot, though. You might think about swapping the cassette instead, from a 13-26 or whatever you have now to something like a 12-24 or 11-23 (I'm guessing at the specific numbers because I've never, EVER needed higher gears--I've been engaged in a 10-year quest for lower ones). That would be essentially a bolt-on, and cassettes are available everywhere.