Could someone help me on how to raise the action on a tune-o-matic bridge because there is some fret buzz.

There are two screws on either side of it. One towards the low e and one towards the high e. Loosen them and the bridge will rise. Tighten, and the bridge will lower. Don't loosen them any more than you need to though. You don't want your bridge ripping out of the guitar.
Quote by Led Zeppelin45
I've got a gig coming up in a couple of days should i wait and do it after that.

Nah, bridge adjustments are very minor if you do them right. Just remember to do the same thing to one side that you did to the other, just like algebra. You only need to usually raise it a fourth or half a turn any ways.
Quote by Led Zeppelin45
How big of a chance will there be screwing it up?

Very little. It's really straight forward and simple. Just DON'T overdo it.
Don't forget to play with the height of the tailpiece as well. Lower and you will have tighter tension on the strings, higher and it will be more "loose" feeling. Play with it a bit until you get it just how you like it. You'll have to re-tune after every adjustment.