Yup, 4 guys should be able to lift it with suction cups and place it back on your new base without much of a problem.. I still say put down some vegetable oil just so you can slip it around if it's not EXACTLY on.
How long? I honestly couldn't tell you. The size of that tank alone would scare me, simply because I don't have 4 guys on standby to help me move it around
However removing the silicone while labor intensive, not too long, just enough to remove the bottom pane remember, you want to keep those sides as strong as possible! If you have the glass/PVC bottom no problem. Putting it back, Re-bracing so you can remove all the silicone, labor intensive x 4! But all the above if you had the bottom in place, could be a weekend job.
I would take a lot of care in making the re-silicone job go good, so a minimum of one weekend just to set everything else back up and resilicone with Dow 995.
The cure process could take a while though, not sure exactly how long, but for a FULL cure, more than a weekend.
Then (and I didn't mention this above) fill it with the hose after you're 100% sure it's cured, and let it sit for a long while just to see if anything breaks/leaks, best in your garage than in your living room!