Getting back up...need some guidance please

Good Evening All... years ago I ran multiple saltwater tanks and then in 2006, my first little man was born. I simplified my system and then simplified some more and ended up settling with an Oceanic 144 gallon half circle tank. While on deployment, there was a meltdown and well, I lost most everything except a few fish. Well, the tank has been running with live rock, flow, even the two Tunze's pushing water for almost 10 years. I was going to sell off all of my gear until recently. My kids are now old enough to enjoy and my wife, she is either use it or sell it. So, I've decided to get back up and start again. I just updated the firmware on my old trusty Neptune AquaController III Pro. Clearly all of the probes will require replacement. I would estimate there is 80 or so pounds of rock, Giesemann Infinity 48" (2) 250w HQI + (4) 54wT5, Deltec AP701 Skimmer, Deltec PF501 Calcium Reactor, Deltec FR616 Fluidized Reactor and a Deltec KM500 Kalkwasser Stirrer. So, no need to purchase any new gear, just replace some old parts etc... Ok so this is where I need some guidance. Where do I start? I originally had a small sump below the tank and now I've decided to place the sump in the crawl area below the tank - easy day. My question is should I turn back on the skimmer, perform a water change, test conditions... I would appreciate some help on this one. I would assume the rock is still living, my sand bottom isn't really there as much however I would have to believe I still have good bacteria etc... Thoughts??? Thanks so much!