I have the same boat with Volvos. Same situation, can hardly see the pump. The answer is, it's a lousy job. I used one of those cheap CVS round counter top mirrors and rested it under the pump so I could see it. Armed with 1/4 inch drive swivel sockets and long extensions, small open end wrenches and every other tool I could think of to make it easier it was at least a six hour job. My chest hurt for a couple of days. It's been three years so I'm due again but reluctant to do it.
I bar the engine over 1/4 turn every month in the winter so the pump doesn't take a set also installed fresh water flush hoping to extend impeller life...Good luck, it sucks!