providing you have no other problems, or rusty bolts, yeah, the job can be accomplished in a couple hours,
if this is your first time doing this, i would plan on at least double that, tho, maybe longer, depending
if you are smart, you will replace the idler pulleys while you are in there
I've seen them skip without damage. But broken while running, I'd bet on bent valves.
Head gasket job, plus take the heads to a machine shop for pressure testing and valve replacement as needed.
Pretty easy to put a new belt on. Turn it over by hand to make sure it's not binding and then start it up.
If it has bent valves it will not be running like a good Subaru should.
Bent valves can be taken care of, but it's a bit more work to pull the heads. I'd pull the engine at that point.