I think you can do it. Use your rides during the week simply to maintain your fitness. Go very long on one weekend day and use the other as a fun spin/recovery ride.

You didn't say what your current long ride mileage is, but if you did a 65 miler last year I am sure you can work up to that easily. Get in one long ride of 75 - 85 miles before the century and you're set.

Sue is right, it's almost all mental. If you want to do it and you have a good base, and if you pace yourself and eat and hydrate properly, you can do it.