Welcome to the forum!
Whole body weight training 3 days per week would be a good place to start for maintaining muscle mass while you lose fat. If you're wanting to be in the gym more often, then try doing a split routine. For cardio, interval training a couple of times per week is favorable over low intensity cardio in terms of maintaining muscle mass. When you are doing anything at a high intensity, you need to allow your body adequate recovery, which is why interval training is not something to be done everyday, for the average person. Outside of those two things, try to be as physically active as possible by going walking, hiking, swimming, cycling, or whatever it is that you enjoy.
What is your plan for nutrition during weight loss? Here is some reading that I would suggest for answering some of your nutrition questions: http://weight-loss.fitness.com/t/55758/please-read-nutrition-101-article