Scannerz just gave my MacBook logic board a big fat F!

I upgraded from Snow Leopard to Mountain Lion about 3 weeks ago. The system was running short of memory so I upgraded it. The system was running fine for about 2 weeks.

Yesterday the thing started acting erratic. A lot of spinning beach balls, delays, and then some errors saying files couldn't be read to or from the drive. I figured the drive was going because the system is over 3 years old. I ran Scannerz on it and it indicated a lot of errors and irregularities. I rescanned it in cursory mode, and none of them were repeatable, just showing up all over the place in different regions of the scan. I went through the docs and they implied either an I/O cable was bad, a connection was damaged, or the logic board was bad.

I tossed on my backup of Snow Leopard that I cloned from the original hard drive because I figured Mountain Lion was to blame and booted from the USB drive with the clone on it. It wasn't. I performed scans on every single port, and errors and irregularities that couldn't be repeated were showing up on every single one of them. I then, for kicks, put a CD into the CD player. Scannerz doesn't test optical drives but I figured surely that will work. No it won't. More spinning beach balls and messages telling me it can't be read. It was working fine 3 days ago.

I know a lot of people don't like MacBook's, but mine's been great, at least until now. It was working great even with Mountain Lion after the upgrade. The system is a mid-2009 MacBook.

In my opinion, it's a complete waste to toss this system. The display is too good, the keyboard works great, and it still looks good, plus this type of MacBook still uses the FireWire 400 port and I use that for Time Machine backups.

I've tried reseating the RAM, it didn't do anything. I shut the system down and put in the old RAM, booted to Snow Leopard, and the problems persist.

Here are my questions:

1. The Scannerz documentation somewhere said something about the Airport card not being seated properly, but when I go to iFixit, it's apparent, at least I think it's apparent, that this isn't a slot type Airport card that the user can easily install or remove. If the cables or connections to the Airport card are bad, could they be causing this problem.

2. How about any other connections that can be intermittent, failing or erratic?

3. Any type of resets that I could possibly do to get rid of this?

4. For any of those that have replaced a logic board on a MacBook, if this really is the culprit, are there any "gotcha's" I need to be aware of?

As an FYI, I replaced the hard drive on an old iBook @500MHz that I had a long time ago, and I replaced the drive on a 1.33GHz PowerBook about 6 years ago. You have to be careful, but using some of the info on web sites like iFixit it's not that hard. Time consuming, but not that hard. The Intel based MacBook's to me look like they're easier to service than either of those.

I'm thinking about getting a unit off of eBay that matches mine but has something else wrong with it, like a busted display. I REFUSE to buy a new system. A guy at my office has a 2007 Mac Pro and he can't upgrade to Mountain Lion because his system is "obsoleted." That's ridiculous. If you pay nearly $7,500 for a system it shouldn't be trash just because Apple decides they don't have enough money (sorry for the soap box, but it's true, IMO!)

Any input is appreciated.