Yes, it's under the flooring in the trunk.
Replacement is easy. Any Group 48 battery will be fine. I used a WalMart Everstart 48 for $77. Got top ratings in Consumer Reports. Be sure to connect the vent to the hose.
Also looked at Costco but for some reason they didn't have that size.
Dealer wants $400!
Even my mechanic, whom I trust, wanted over $200 (because the Interstate recommended replacement is $160).
Sears DieHard and AutoZone replacements are $140 or so.