If you've been experiencing sluggish turnover, and now no turnover, it sounds like the battery is pretty much dead.
Spend the extra money for the optima red top. You won't be disappointed.

I've used many, in several different vehicles. They'll last forever, they don't leak, you can mount em upside down, sideways, any which way you want. Most have sideposts, for multiple applications, which means you can use side posts for your aftermarket accessories, so you don't clutter up the two top posts with a big bundled bunch of wires. Keeps things neat and orderly.
They're compact, and will fit well in the 240 engine compartment. If, by some miracle, you manage to drain an Optima completely, you can recharge it... and it'll actually hold a charge, unlike most conventional batteries.
Optima usually comes with a very beefy warranty, and with good reason. They rarely if ever go bad. Buy one, and I'll bet you never replace it as long as you have your car (assuming you don't have a draw, draining juice from the battery)
Any shop that sells batteries better damn well have a diagnostic device to test for a draw. When you go to buy the Optima, ask if they can test the alternator for you.