Having Various Problems with MacBook

Hi there everyone! first off thanks in advance for any help!

So heres my problem: Ive got a Late 2008 MacBook (Aluminum) and lately it has been acting rather erratic.

OS X 10.7.3 Lion
2.0GHz Core2Duo
4GB (Aftermarket) RAM
320 GB (Aftermarket) Seagate 7200RPM HDD
13.3" model
everything else is standard

Rundown of the symptoms-
-Certain programs start extremely slow and then run slow once they start.
-Computer itself starts up extremely slow. usually i starts in ~20-30 seconds but lately it doesn't finish booting for 1 and a half minutes.
-Disc utility turns up a corrupted boot drive and needs repair. once repaired it runs fine awhile then needs repair again a few days later
-Finally, today, a kernel panic. Booted up fine after.

I've been told before that this is a drive failure and there are bad sectors that keep getting written. I think this probably is the problem, but i dont know if that would cause a kernel panic. Can someone lend their expertise?

**Computer is fully backed up, and i've had to restore from a backup multiple times. This usually gets it to work for a while, but it eventually starts failing as usual. BTW, after the kernel panic, i restarted it and checked disc utility for corruption. The drive was fine. This is why i am believing there are problems other than the drive.

Thanks for any and all answers!