I'm with Tom Lee. Try to fix it first. If you aren't used to these types of repairs and want to keep using it while you get up to speed, the answer to your last question is: yes, you can replace it with an analogue board from a Plus. But definitely fix the old board, please just don't throw it out.

FYI, you can also use an SE analogue board for use in the 128K-Plus as well. I haven't tried a Classic board yet, though theoretically, it should work as well, with a similarly modified logicboard cable.