Newbie, 3 weeks out seeks your thoughts on reasonable exercise goals

 Hi, all . . . 3 weeks out tomorrow!  Feeling great, but not losing in the last week or so.  Down 7 lbs since surgery, but lost 34 lbs prior to surgery.  I have 76 pounds remaining to lose.  I have been walking the hilly neighborhoods around my home to the tune of about 2 miles a day for the last week and a half.  Joined the gym today so I can exercise even when the weather is bad, which is often here in Seattle.  Can you share your thoughts on the best exercise routines for a newbie?  I am just gearing up to get back to work (full time, but administrative).  I also go to school full time, so I have one hour early each morning to devote to exercise.  I am planning something like this:  20 minutes treadmill at 3.2-3.5 mph with on and off incline; 20 minutes eliptical or exercise bike; 10 minutes warm up and 10 minutes cool down . . . Any advice, tips or tricks you can throw my way would be much appreciated!