Make sure you take a couple minutes and look for the rating plate in that boat, if it exists it should be back on or near the transom somewhere. I'd be very careful about hanging a 25 HP motor on a 12 foot boat, as it may not be rated for 25 HP. Some 12's are different than others, more depth, more beam, etc. so the motor ratings can vary.
Proceed with caution.
25 hp will be plenty for 12 foot boat with any amount of weight added. I have no pics, sorry. As stated really easy to do, your buddy should get er done in under three hours. Don't spend a lot of money on the boat seats, I bought the cheap ones then added a outdoor chair pad for comfort.
I was out there on opener as well and caught a lot of small fish. Averaged about 30 walleyes a day but nothing bigger than 17". Last weekend the bite was a lot tougher which I would assume was due to the weather.