If he came in a cup, just scoop him up in there with some water. Or you can find a small container/tupperware and put him in there while you change the water.
I doubt that you could lift the tank with all the gravel, decorations, and more than 50 pounds of water.
So first, do you have a gravel vacuum or a turkey baster? Use those to stir up the gravel and pick up the debris that's stuck...then you'll want to get a siphon and start sucking the water out into a bucket. Once you've removed all the water, replace with clean water. Try to make the new water match the temp. of the old water as closely as possible. And, obviously, you'll have to treat the new water with water conditioner.
Also, you'll want to occasionally (maybe monthly or so) remove all the decor and rinse it under hot water. I used a toothbrush to scrub them too.