I am thinking about getting into rowing at home and have a few questions. I have tried rowing in the past at gyms and it seems to be the one cardio exercise I enjoy doing. I am about 167lbs, in decent shape and do some light weight training 3-4 times a week, nothing major. I have been looking at getting the Concept 2 D model for home use. Here are some questions I have about rowing:
1. As a new rower, how often should I row to begin with? Is there a basic routine for the first few months? Some of you can row for hours a day and I don't think that would be me, well at least for now.
2. My initial plan was to row 3-4 times a week when I am not doing any weight lifting, would these be a good idea?
3. I like the fact that rowing works many muscle groups but can it also help to increase muscle mass a little too? I am not looking to bulk up with rowing, but more like get toned (I hate that word) and a bit more defined, maybe even help loose my tiny gut

Any general information would be helpful since I am such a noob at this.
Thanks everyone.