am3gross: I got the idea from
this thread on RC. I hope to get addicted with this smaller setup so I'll save every last dime in order to make my dream tank happen.
three-spot: The bit-set cost $5.97 (+tax) at walmart it includes 2-diamond tipped bits; one for making starter holes and one for doing the actual cutting. Make sure you have a 3/32 collet (a standard-sized changeable fastener sorta-thing) for your rotary tool otherwise the bit won't fit right. You can pick up a collet set at Walmart that includes the correct size for $6.97 (+tax). The bulkheads cost 4.99 (+tax) at my LFS.
LobsterOfJustice: I wasn't planning to keep the heater like that; I just sorta threw it in there when I got it. I'll probably keep it in the middle of the rubbermaid away from the sides.
Landon B. and specialkb: Thanks for the support!