1. For the first 3-4 weeks you will get a workout, but after that your body will adapt and you'll be fine. This was my experience after not cycling in January and February (Toronto), and then re-starting in mid-March/April.

2. Sweating will not cause you to stink: if you shower at home before you leave, and your skin is fairly clean, then there will be no/little bacteria to cause smells by the time you arrive at work in the morning.

3. How much you sweat is up to you: if ridden at a leisurely pace (after the above few-week 'shape-up' period), you probably will not sweat. If you want to get in some cardio, then you will sweat more (but still not stink, if you pre-shower). If want a work out, you can also wear 'workout clothes' for your ride and change in a bathroom stall.