Ironic that a Wichita guy is asking about the Boundary Waters and a Wichita guy is the first to answer. So, I'm sure there are many people with MUCH better info than me.
I've been several times, and I've absolutely loved it. Besides the rolling plains of Kansas, the northwoods is one of my favorite places. While you don't need a guide with you if you can read a map, I do suggest that you work with an outfitter who will provide several key services: equipment rental, advice on where to go, assistance with permits, canoe transport, shuttle, menu planning, etc. There are many. I would also suggest that you get on it quickly. Not all access points are the same, and permits are limited in quantity.
You'll need to be in decent shape. Even the lightest of modern canoes can get heavy over a longer portage with some elevation change. Also, sitting on a canoe seat all day can hard on your back.
Finally, you're calling this a "Fishing Trip". I've fished every time I've been, and the fishing can be great. But, I'm not sure I'd call it a "fishing trip". In my mind, it's a canoe camping trip with bonus fishing. If someone asked me to suggest a destination for a smallmouth/walleye/northern/muskie/etc. fishing trip, I'd suggest something that involved hot running water, electricity, and outboard engines. The whole camping/paddling/portaging thing consumes a lot of fishing time and a lot of energy. You can decide that for yourself, though. That's nice the thing about the Boundary Waters.