For us, the $25 for the SunPass transponder was worth it - we always rent a car, so I've gotten a lot of use out of it. I love not having to stop for tolls.
From MCO, we always take 417. Follow the signs at the airport for 417 South. You'll be on that road for about 15 minutes or so. Take exit 3 for World Center Drive/Epcot Center Drive/SR 536 - I think that will take you right to Buena Vista drive where you turn left, then turn right at the intersection at the giant Hess Station onto Epcot Resorts Blvd.