Looking good!
I would strongly suggest against putting a shed under your deck.
As for the gopher, there's many way people say you can get rid of them. A couple ways include:
Drowning them (I've killed one in my backyard this way). You have to find one of their burrows, and shove a hose clear down it, then turn it on and let it run. A lot of time sit doesn't work, and it can potentially make a huge mess of your yard or your neighbors yard. Be prepared for them to pop up one of their other holes.
Poison them. Usually want to have a company come do this. Probably one of the most effective ways to take care of them.
Suffocate them. Some people use propane, some use the exhaust from your car, the effect is the same, it depletes the oxygen in their burrow and kills them. Be prepared for them to pop up one of their holes (you should clog as many as you can find so it's more effective)
Get a gopher snake and release it in the burrow. A single snake can clear many many acres of land. Quite effective but snakes give me the heebee geebees.
Ofcourse, the most fun option is a .22.
Obviously not really viable at your home.
I've been dealing with gophers in my yard for the last few years. I've only been able to knowingly kill a few. I now have a company that's supposed to be taking care of them. They aren't doing a good job up to this point