Rondo

I've got a 97 3.2. Got a new battery about a year ago, last winter it started giving me intermittent problems starting. no start if ac/radio on, slow start if everything else turned off. Took it back and got a replacement a month ago, but still having problems with the battery. Figuring I just had bad luck, took it back to AutoZone to see if the 2nd batt failed, but everything checked out when they tested it this time. The autozone guy pointed out some pretty funky corrosion building up behind the ground terminal. Questions:

1) is it worth trying to clean? It's in there between the individual wires, so not sure how effective trying to clean it would be.

2) How much of a pain is it to replace these cables myself? Not sure if I should just replace the ground or do them both. I'm all thumbs with car repair, but willing to try it if it's a simple fix & doesn't require getting under the car (which I have no place to do).

3) is there anything else I should check in addition to the cable? The autozone guy said alt./starter/battery all checked out good. Any suggestions are appreciated. Thanks!