yes square taper is/was the standard until a couple of years ago so you should have no trouble finding a crank. just get the crank first so you get the right size chainring. there are two sizes of swuare taper though but it shouldn't be much of an issue with mtb cranks.

It would be really nice if the fame has horizontal dropouts but it's not necessary. If it doesn't you'll probably need some sort of chain tensioner so keep that in mind