Resurrecting this old thread again- I took the battery to BatteryPlus and after charging it, they said the battery was fine. It shows 510 CCA (instead of it's marked 550), but it should be fine. The kid yesterday when I dropped it off said it was reading 12.0volts when he put a voltmeter on it and told me to not have high hopes. Unfortunately today, he was with a different customer as the kid I got today wasn't extremely helpful- he plugged in a portable machine, it did it's thing and he said it was showing good.
So that's where I'm at.
I did measure the compartment/battery box. Strangely, there's a huge amount of storage space down there, but only a small inset for a battery (12"x7" and maybe 10" tall).