Here is a tip, forget the class. Force yourself to go to the gym everyday ( no skipping for even weekends ).
With my Job of programming sometimes I get into my work and skip the gym for several weeks.
This of course leaves me looking like most programmers ( either really fat, or really skinny ).
pick one of these machines ( stair machine, elliptical, treadmill)
If you are still recovering from your surgary, I would recommend the ellipitcal first, as it would be a low impact on your joints. If you are more out of shape and not injurred go right to the stair machine, or treadmill.
The worst mistake people make is they decide they are going to do something without setting mental goals. Tell yourself what you are going to achieve today. Then push yourself to achieve it. Set your goals to something very easy the first day. Then every day after increment your goals to a level that exceeds the previous day. After 90 days you should be able to do a 1.5 mile without any problems. If you have any doubts take some ephedra the day of your test( not for your workouts! ), and you will beat it with flying colors.