Yep, an HOB without the bio insert is okay. The dimensions of the aquarium sound fine, but keep in mind that you are going to want thick glass, especially for the bottom pane, and while 1/4" glass is easy to find and cheap, getting 3/8" glass for the bottom pane could get expensive. 3/8" is also a lot harder to cut.
I don't know of anything in your area, so I'd just do an online search for a local club and/or ask your LFS. Is there one in your area listed on this web site?
If you want to build your own live rock, I suggest you visit
www.garf.org The PVC inside the rock might inhibit the ability of the rock to be porous and become live, but I'm not sure. Usually people recommend you do 1 lb homemade rock to 2 lbs live rock, but you can go with all homemade live rock and add a couple of good live pieces of rock to get it seeded. The more homemade rock you have, the longer it takes to become live and provide adequite biological filtration.