From MK to Epcot is very easy
Via monorails -- walk out of MK and toward the right are the monorails - take the Express Monorail to the TTC...walk off there and follow the signs to the Epcot Monorail - VERY VERY EASY
or
Walk out of MK and take the Ferry boat across the Lagoon to the TTC -- walk off the boat and look to your left - there will be directional signs stating which monorail goes to Epcot - again very easy!
From MGM to MK there will be a bus to the TTC and then you can take the monorail over or the ferry boat. You could also take any of the buses to the Grand Floridian, the Polynesian or the Contemporary and then monorail or boat over (from GF or Poly) or walk from the Contemporary.
Hope that helps,
Liz