Yes, your primary concern is whether the battery will fit in the space provided in your engine compartment, and the next concern like MR2Jedi mentioned is to get more cold cranking amps if you live in a place where temperatures drop below freezing. Buying one is a no brainer going to places like Pep Boys or wherever where the store clerk will show you a list of batteries available in the size you want and how many CCAs they have. Your only other concern when you purchase is to make sure your battery is fresh by checking the manufacturing stamp on the top or side of the battery (depends on brand). Do a quick Google search for how to read the date stamp on a battery.
You know, Russ, you're right. I ought to add that to the Highlander stickies at least....