Replaced hard drive bracket. Now MBP acts like an "infant"

Hello Everyone! A month ago my MBpro had some error message and immediately turned itself off. Then when I powered it back on, I just got a grey screen with the icon and a status bar, but it got stuck there. I took it to the Genius Bar and the gent there suggested that I replace my hard drive bracket. Since this is a mid-2009 machine, Apple didn't have the part. So he told me to buy it new online from a 3rd party provider. I found it on Amazon for about $30. We replaced it and it started back up again. However now I keep getting messages that my browsers are out of date. I ran the "software update" several times and it says all is up to date. Firefox won't run (just a blank screen when it opens) and neither will Chrome. Safari is the only one, but I get warning messages from sites I visit that my browser is out of date. Also, the thumbnails I see on my desktop will not display when I open them up in "Preview". Any ideas? My machine stats:

Model 2.53GHz Intel Core 2 Duo

OS X 10.6.8

Safari 5.1.10