Hanna makes a good TDS meter. I don't envy you with all the work you have ahead. I agree, that the stirring of the substrate probably released a lot of nutrients and toxins into the water column. A 10 yr old sand bed would probably be getting ready to be changed out anyway, at least according to the current theories on DSB's anyway. There are several ways of doing what you're gonna need to do. Get some large rubbermaid tubs and put the corals, fish and rocks into them, with heaters and powerheads for circulation. Then using iether a large scoop, remove the old sand. YOu will make a heck of a mess in the process, and probably won't be able to see more that a few inches after a scoop or 2. The other way would be to use a piece of hose and siphon the sand out. The only problem I know of with that is the loss of water. You'd have to keep replacing the water as you siphon out the sand. I'd certainly recommend making sure you have everything out of the tank before you start, to eliminate any chance of losing anything to the siphon process. Once you have all the sand out, clean the tank well, rinse well, and start all over with fresh sand and water. I'm not sure if Home Depots where you are at carry Southdown or Old Castle Caribbean play sand...Worth a look, since it's about $5.00/50 lbs, as compared to $1.00/lb for the stuff at the LFS. Many people would probably recommend replacing all or part of your live rock at this time. I won't go there, not sure if that's a valid theory or not, but...
Anyway, you certainly have a lot of work ahead of you. It's possible that you could get away with just running some canister filters full of carbon and a good phosphate media like RowaPhos,and trying to filter out most of the nasties...Might be worth a try before you replace all the sand...