OK, I found out the focusing screen is definitely scratched up a bit, though I may try a blower brush if I can pick one up at the local camera shop. A bit of an internet search reveals that you should never use any fluid to clean the focusing screen, since it can get sandwiched between the two plates of the screen. I may try buying another, but that looks like an expensive replacement. Not to mention that there are tons of model numbers and I can't seem to find an index of all of them.
I'm off to try to complete my second roll to double-check that my film back indeed works.