Craigslist is a good place for deals on used equipment. Also if you have any local aquarium clubs (or reef clubs), you can find equipment that way also. For the most part, if you find a used tank, there is often a stand involved as well. And typically extras as well.
I have yet to have a problem with a used tank leaking - actually, the only one I had that leaked was purchased new... I've gotten 3 used tanks with no leaks ever, and just filled up a 4th (75g) used tank which is doing well so far. With any sizable tank, used or new, it is prudent to fill it up either outside or in a garage, etc. first to double check for leaks - I usually fill up a tank and leave it overnight before setting it up in the house.
The internet can be your friend as far as good stands go, as well. I was looking at R&J enterprises and Deep Blue stands with my 40B - got Deep Blue and it was built like a tank, though the description was a bit misleading so I had to modify the back. I have also found a few nice stands on clearance at Petsmart when they are discontinued / missing the tank. Obviously that method is hit and miss, so it depends on whether you're taking your time or in a rush.
Acrylic is lighter than glass, more expensive, scratches more easily, often thicker, can be made in any shape.
Glass is heavier, more resistant to scratches, typically cheaper.
Depends on what you are going for. I believe most people go the acrylic route if they are getting a very large tank (for ease of transport, being it is MUCH lighter), or if they are getting some kind of custom curved shape. I've only had glass and have no complaints.
Also if you're considering a 55g, do yourself a favor and look at 75g instead - same length but an extra 6" in width makes it much nicer to work with and aquascape.