First off, these are NOT stupid questions.
"is dealer bought driftwood ok in a freshwater community aquarium?"
Absolutely. Actually it's safer then found driftwood as it's already been sterilized. Do not that you will most likely have to soak it get it to stay on the bottom of the tank. Note, driftwood can alter the pH of your tank
"recommnded freshwater test kit....any opinions?"
Personally I like the "Quick Dip" testers but Jungle because they are quick and very easy. I also have "Fresh Lab" by Red Sea which was highly recommended but not as easy to use.
"also going to use black backround and modulator controlled moon lights (should look awesome)"
These do sound neat but are they going to give your fish enough light since they emulate moonlight? Also, if you have plants you will need more light.
"Aquarium guys have a black onyx, but it says it has a slight buffering ability....not sure what that means and is that safe?"
From what I've read TRUE onyx should not alter your water chemistry. However, not everything sold as onyx is the real stuff. Check out fins.actwin.com/aquatic-plants/month.200107/msg00401.html
"Also not sure what is the correct pH for a community tank with mixed species....do I strive for 7.0 to make all fish as happy as possible? (Going to do the usual mix of small fish, plus a red tailed shark if I can find a good one..a pleco and a couple of angelfish)"
Before you stock your tank do some research to make sure what you want will be compatible. 7.0 is a general pH and should be OK but don't stress too much about the pH unless it's way off. Also, be careful not to overstock your tank. Plecos get HUGE and angelfish get tall. Good sites for fish research are www.LiveAquaria.com and www.BadMansTropicalFish.com.
One other note, you didn't say if you've had tanks before so this might be obvious but don't forget to cycle your tank BEFORE you stock it. You can find instructions for fishless cycling at malawicichlids.com/mw01017.htm
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PHLaure