417 is not always faster as it veers east of Orlando and is not a direct route to WDW, as recommend by pp the best course of action is to follow the GPS route that populates when you arrive in Sanford, if it takes you via I-4 then I recommend following that as I-4 is truly the most direct route between Sanford and WDW..
From WDW to KSC, you would take I-4 to 528 east and take 528 straight to KSC.. As mentioned by pp follow signage to the KSC visitors complex and it should be an easy drive..
From WDW to Universal, take I-4 east (towards Orlando/Daytona) straight to Universal area and following electronic signs to parking garage entrances.. Once again, also an easy drive..