Determine from your amount of priming sugar the number volumes CO2 you have in the beer.
Determine your kegerator (well, the beer's) internal temperature.
This will give you your pressure needed: http://sdcollins.home.mindspring.com/ForceCarbonation.html
FYI, 1/4" lines at only 5' will be too short (many people on this forum suggest 5' is too short even for 3/16"). Are you sure they're 1/4" lines? A lot of times, it's 3/16" line that's fitted onto a 1/4" barb. You might want to check this. If they're actually 1/4" ID, buy some new 3/16" ID lines while you have the chance before you assemble it or you'll be pouring lots of foam.