2001 V70 2.4T Clicking noise/engine won't start

[[mas]]

With the recent heat wave, my car's been acting weirder and weirder. First, the AC comes and goes, and last night the ABS/STC lights come on (which they haven't done since I had the ABS Control Unit reconditioned). This evening I go to start the engine, and it turns over with massive hesitation, and the engine feels noticeably weaker. Then the ABS/STC lights come back on, and I pull over to the side of the road and turn off the engine. I go to turn it back on, the engine makes a clicking noise and fails to turn over. On the dash, every single light is lit up -- STC, ABS, oil pressure, etc.

Help! What's going on here? Is there anything that can be done by a relative novice, or is this going to cost me some major bucks at the mechanic?

[JRL]

BATTERY

[[mas]]

If it's just a battery then it's much better than I thought. Most of the time the dashboard lights up like that, I find myself several hundred bucks lighter.

Thanks for the reply, JRL!