Is there only one screw holding tank in place? Does radiator have to be drained completely? Or can you partial drain and remove recovery hose from radiator and remove it that way?

Just the one nut on top, I think. Why are you taking it off? If you just need to get it out of the way, leave the hose connected and move it out of the way. If you need to take it off, I forget where the hose leads to. High or low on the radiator? What I woudl try to do is hold the tank up high after you've removed the nut, over a small bucket, remove the hose from the bottom, drain tank and some from hose, then keep the end of the hose higher than the radiator. That'* what I would do to avoid draining the radiator.

Dirty coolant tank. Water pump went, put some sealant in tank to get me home. Now have difficulty seeing coolant level, plus it looks nasty.