Drill holes for overflow

[PaulCheung]

I have a 50 g tank and would like to drill 2 holes for a herbie overflow and 1 hole for return.

1. What sizes of the holes should I drill? 3/4" or 1"?
2. Where can i get the drill bites to make the holes?
3. Where should the holes be located?

I also want to paint the back glass to black. Should I paint the glass first or drill the hole first?

I also need an overflow box. Where can I buy black acrylic in Vancouver area to make the box?

Thanks