I worked a bit from home at around week 3. After 5 weeks I was released to drive and went back to work part-time, starting with 4 hours a day, then 6, then 8, etc. By 8 weeks I was back to working my usual 10 hour days (office management job), and really never looked back. I do sort of miss the free time, though. . . but I do remember being quite tired after the first few half-days.
As for long car rides, as long as you're the passenger, it depends upon how you feel. Try starting out with modest distances, then lengthen and see how you feel. You may want to keep a pillow across your chest where the shoulder harness crosses, but generally you should be fine. I personally would suggest that if you're contemplating a cross-country drive, try to stop every couple of hours to get out of the car and move around a bit to keep your blood flowing, etc.