Take pictures of your progress and post a DIY. It will be very informative on how to take tanks apart and re-assemble them. (I hope that is what you are planning.) When you take the bottom frame off, you will find that it isn't as simple as just tilting the tank. You will want to take the bottom panel off and move it flush with the adjacent panels. Some LFS's will be helpful in ordering the framing parts for you, but I have found many don't want to be bothered with the hassle. It comes in straight strips that you cut with a miter saw (for good angles). You can also use wood trim from Lowes or HD. Just make sure to seal all the edges and the inside with polyurethane before attaching them to the tank.
If your tank bottom turns out to be thinner than the rest of the tank, it will be a sure indication that it is tempered. Make a mental note to not drill that piece if it is. Most tempered glass has a printed note in a corner in white lettering that it is tempered. It also warns against cutting or drilling. (not always the case)