Try waking up in the morning and doing 20 minutes of stretching exercises, situps and so on. If possible follow up with a 20 miute or so walk an walk very rapidly- before breakfast. Three times a week get to a place where you can do some road work: start with 3-4 3min. rounds, alternating jogging, running and all out sprinting during the round and walking very fast during the rest. In the gym warm up with a couple rounds of fast and serious shadowboxing, then 3 rounds on the heavy bag, 3 on the double end bag and acouiple on the speedbag.
I would suggest that you begin the exercising and roadwork a week or two before goin g to the gym. Once there you shoud be ready for some light sparring in @ 3-4 weeks maximum,