Well I finally replaced my battery.

About a month ago, took the computer to the Apple store. Signed up for a Genius Bar appointment, was all set to go. The guy did diagnostics on my machine and everything (except the battery) looks great. He did note a few nicks on the outside here/there. Battery level was I think 40% or so.
Then he says to me, "Because your computer is so old, we don't carry that battery anymore."

He did seem extremely interested in the computer and commented how they are in high demand. "If you ever want to get rid of it, you can get about $800 for it." He thought that was about what I paid, but that was closer to $1500. Since it is lightweight and has full USB ports (and Firewire) people like this model.
He gave me information for a local shop that works on Macs.

I was a bit frustrated that I wasted my time to go through all of that, pretty much for nothing.
Didn't think much of it, and didn't do anything. Then last week the fan on my computer started running almost all the time. Just wouldn't shut off unless I powered off the computer.

So I ordered a battery from Amazon on Wednesday. $59, with free 2-day shipping with Prime. Battery arrived yesterday and had it in my machine in about 10 minutes. It came with 2 screwdrivers that you use to open up the computer, take out old, put in new, and close it up. Was so easy, don't know why I didn't do it sooner.