I just changed mine a couple of months ago and I didn't have to remove the overflow or washer bottles. It will be easier if you do, but not absolutely necessary.
The most time consuming part of the job for me was scraping the old gasket material off the block. Also cleaning the bolts took me a while, I did it by hand with a wire brush but a bench grinder with a wire wheel would be quicker.
I used Ultra Grey sensor safe Permatex on the new gasket and on the water pump bolts. Some of the water pump bolt holes are open to water jackets in back and will leak externally if not well sealed. I let it sit for a full day to cure the sealant before I put coolant back in it.
When mine failed there was no play in the hub, it was leaking out the bottom. It wasn't anywhere near the gallon a day that you are experiencing, but it was enough to notice. Then one day on the way home, it really let go. So you won't necessarily feel any play by wiggling the pulley, but if you do it'* a bad sign.
1990 LE -wrong bumper