How hard is it to change out an undermount sink?

Question

assuming the sink is stainless steel so light weight, mounted under granite.

Answer 1

Not too bad.  About an hour and a couple busted knuckles, if you've never done it before.  If you look up around the edges of the sink bowls from below, you'll see little clamps (probably 2 on each side and 3 in the front and back).  They're generally held in place with screws.  You might also have the type of sink where the screws just go right through the lip of the sink into the granite, but it's doubtful.  In any case, just disconnect the supply and drain lines with a wrench (remember to turn off the water first).  Then undo all of those screws, and the sink will drop right out.  Reverse the process to install a new one.  

Before you do anything though, make sure you find a sink exactly the same size as the one you're removing.  Granite can't exactly be trimmed to fit a new sink...