Your better off having a glass shop do it. a few considerations though..
- a glass shop wont guarantee that they Don't break it
- most tanks bottoms are tempered and you/they cant drill that.
- If you want a drilled bottom you have to order a special non tempered bottom
- some good LFS (local fish stores) can drill the tank
Out of 10+ holes I have had drilled they (glass shops) never broke a tank on me and charge$10 - $15 per hole
most important is to bring the fittings with you when you do have it drilled
Simplified Reefkeeping