Can the apple store update the firmware etc

I have a macbook 2.4 alu (Late 2008) and Installed linux as soon as I got it.(I just like the cases). Anyway I know that you need to use apple update in osx to update the firmware.

I can't dual boot because my HD is MBR.

I thought of 2 ways.
A. Install OSX onto a usb device (Cost 30-40 bucks for usb)
B. Take to apple store, Maybe they can do it.

I can't dual boot because my HD is MBR.

I heard the new firmware updates stop alot of issues.

Well whats the minimal snow leo install.

Because I only have a 8gb flash drive.