Down riggers.. Yeah. You should be able to.
Fish finder. Im partial to the humminbird ones.
Tolling motor. Yes, but I would spring for a 30 lb thrust Minn-kota or similar. A front mount troll wont work for you in this case. (I also reccomend a separate 12v deep cycle battery)
Not a bad little boat I must say. If you need help with that Johnson (which is an evinrude) just go to
http://www.iboats.com/forums/ Pretty good folks over there, but mostly american.
Other things you may want is you PCL (Pleasure craft liscense), safety kit.
Beyond the regulations I also carry:
2-5 pound fire extinguisher.
50M boyant line
A ration pack or 2.
Bottled water.
Spare Keys attached to a floatie.
First aid kit
Spare set of plugs, and a lenght of air line tubing.
Earmuffs for flushing the motor.
Spare prop, crown nut and cotter pin.
HAM radio (ok, its overkill, but...)
Cheers!