Fusion should be able to do it, but be warned, it sounds like you are in for some heavy duty rotoscoping to remove the bear from the original scene and comp it into the new bg.
Depending on how much green grass is surrounding your bear, you might be able to key some of it out, but I'm guessing you will need to do some roto work.
Track the bear, draw a mask for the bear, and link the mask to the track. This will get you started in the rotoscope, but you will be doing plenty of tweaking after that stage. Usually for roto's like this, it is better to roto the object in parts...like a marionette. (Head, left front leg, right front leg...etc, then combine all those masks together, and fill in the gaps at the end) Trying to do it all in one shape is not the way to go.
For the fence removal, it depends on how static the shot is. You will probably still want to track the plate, create a clean frame with the paint tools, and then comp it in using the track information, back onto your original plate.
Again, all can be done with the tools inside fusion.