I bought a new battery for mine last year (same exact model, 2.4c2d), fortunately it was OEM, but the seller is no longer pushing products on eBay. I don't think I'll ever find another official Apple battery for this.
The cracking in the photo around the hinge mechanism is among one of the parts I've replaced called the clutch cover, ran me about $25 for the part. I've upgraded mine to 8GB of ram and installed an Optibay in order to get two SSDs (removed the optical drive, SSD in its place). When I buy a new laptop, which should be soon.. this computer will be around as a backup for quite some time. The only regular maintenance I do on it now is cleaning the fan. On a second MagSafe, as of a month ago.