Rough probability for tools needed (that you may not already have) is: Frame fixture and barrel wrench - 100%, Lathe - 100%, skills and experience in turning barrel ends (at forcing cone) so you don't mess up the barrel/shroud/frame interface and end up with a proper sight picture as well - 100%. Of course, you could get some practice with that setup, and you may end up with a snubby (only kidding, sort of). The cost of the tools alone will far exceed the cost to have it professionally rebarreled. Here's another consideration - the 27 has a high polish blue, whereas the 28 has a bead-blasted finish, and the gun will look pretty strange if the barrel is not stripped, polished and blued (in fact, the entire gun should be re-blued, if you want the finish to match between the barrel and frame). Evan after that, you'll have a Model 27 with a barrel that is stamped "Highway Patrolman" on the right side. If I were you, I'd keep that barrel on the 27 until I found the right barrel (for a 27) and get the barrel and gun to a competent, skilled gunsmith with experience in these things (and with the proper equipment), or trade the gun (if you buy it) on a 27 with a shorter barrel. Of course, if you're looking for an excuse to buy a lathe, frame fixture and other tools, that's OK, too.
Oh yeah, not only is the 28 barrel a different finish, with roll markings specific to that model, but it also lacks the checkering along the top of the rib that the 27 has. I don't think you'd be happy with the finished result, and you run the risk of turning a beautiful work of art into a bit of a mongrel (just my opinion). It certainly would destroy the value of the gun.
One other suggestion - if you buy the gun, try it for a while with the 8 3/8" barrel, I bet you'll fall in love with it. I sure like mine.
