I think I have the exact same boat. Motor size is dependent on what water you want to run, and how much floor space you want to sacrifice (anything over 6 hp will need an external fuel tank). I've ran a 7.5 hp and 2.5 hp motor on mine. The 7.5 was good for running the lower Fraser and bigger lakes, but was a bit much for the inflatable floor boat. And the fuel tank took up too much floor space. I'm very happy with the 2.5 hp motor for most of my fly-fishing on small to medium sized lakes. The minn kota electric works fine for small lakes too, you just wont get anywhere in a real hurry. If you want to troll with your gas outboard, get a small one. As a general rule, The smaller it is, the slower you can troll.
I have a dual anchor setup, the rear mount is drilled through the transom, the front mount was glued onto the bow by professionals (Polaris inflatables i believe). For a fishfinder, I just run the standard clamp on humminbird 110, and clamp it to the transom. If you lay it out right, you can attach a fishfinder, outboard, and scotty mount (for the anchor roller) to the transom.
I ditched the factory seats, and I use milk crates with homemade seatpad lids instead. It frees up valuable floor space, (you can store lots in them) and when fishing you can just push them out of the way. They also double as storage for my anchors, ropes, and rod holders during transport.
I did make a plywood floor to go over the air floor, and it works well if you plan on doing much standing in the boat. It makes a huge difference in stability.
Another thing I did was take the rubber oar keepers off of my old inflatable boat, and glue them to the top of the pontoon toward the back of the boat. They function as my net holder and keep it nicely out of the way.
If you want to attempt to glue things to the boat by yourself, gorilla glue seems to work well so long as you do it neatly and carefully. I'll try to find a picture of my boat all set up...