Two good questions:
Yes, I ALWAYS put my Multi-port valve in my basement. It's been through 13 seasons already. I always remove the O-ring, lube it with teflon lube, and store it in a zip-lock with all the air pushed out. Still have the original O-ring and it's still soft and pliable. Since my filter's under my deck and has been for several years, there's far less UV worries than before.

I pull the drain plug on the filter, tip it slightly so the drain hole is the lowest point. Then I cover the whole filter with a giant contractor trash bag and duct tape it. I don't let tape get on the filter so I start by taping tight around the top and bottom, then around the body. Finally, I lay a block, like a patio block, over the hole in the top.