Well the first thing you really need to do is keep a food log for at least 3 days. This will give you a good idea on what you are eating.
You need about 2200 calories to maintain you body weight.. So at first you want to shoot for around that number calories a day. The reason being, IF you are doing cardio and hitting the weights, this should burn ~500 calories per session. As for getting started training. Every gym I know of has a beginners workout that they should give you when you start, I know the gym I got to and work at part-time does... ask for that. Also, one of the staff should be glad to show you how the equipment works or how to do a particular movement.