I highly suggest prefacing your jaunt into resistance training by performing bodyweight exercises and, as stated by P-funk, cardiovascular exercises as well. 2 weeks would probably be sufficient to raise your level of conditioning a notch, but longer would probably be a good idea.
Once you start hitting the weights, I would stick to a full body routine encompassing freeweight compound exercises to build up stabilizer strength. Also, I would start with fairly high repetitions (12-15) for a couple of weeks before you go heavier.
Here is the full body routine I often suggest to beginners:
Deadlifts 2 x 8-12
Olympic Squats 2 x 8-12
Bent Rows 2 x 8-12
Chinups 2 x 8-12
Bench Press 2 x 8-12
Military Press 2 x 8-12
Decline Situps 2 x 12-15
Hyperextensions 2 x 12-15
Standing Calf Raises 2 x 12-15
Do this three days per week with a day of rest in between each session. As I said, start with slightly higher repetitions first to ensure you have proper form and you develop the ability to properly stabilize these weights.
Here is a good website that explains the proper form on various exercises:
http://www.bsu.edu/webapps/strengthlab/home.htm
Videos are included, but I highly recommend reading their descriptions.
