Sebago is a great lake for togue and jigging with electronics is definitely the way to go. Fish can be found in many areas of the lake, so I would suggest that you spend some time looking over the navionics charts to find areas that look good. Also be sure to contact Sebago Bait or Jordan's store close to your trip to get an update on ice conditions. Jordan Bay and lower bay usually freeze well by late January or earlier in cold years, but the big bay freezes later and often not at all.
As far as fishing, pack light and plan to cover a lot of water. Definitely doable on foot (that's how I fish it), but I would suggest a smitty sled and snowshoes or xc skis if there is much snow cover so you don't lose mobility.
I won't usually fish a hole more than 5 minutes if I dont mark fish. If you mark fish but they won't hit, try a smaller jig. I've done best by far the last couple of years with much smaller stuff than the traditional big bucktails and Swedish pimples. Bigger jigs and large dead suckers may be better if you want a trophy.