From your photos, it looks to me that you have a threaded shaft pump. If that's the case, you can get a puller for the pulley, and use a bolt and washers/sockets/ to install it on the new pump. Some new and reman pumps don't come with a reservoir anyway, so pulling it off the old pump is required. They come off easily so it's not a big deal....just messy! As for checking for leaks, yes, clean everything up good and check for fresh oil leak(s). If the reservoir is dented or damaged, it can very easily leak around the "O" ring seal. The shaft seals are also a common place to leak. If the pump otherwise still works fine, I'd just reseal it. They're not hard to do.
