I have TMobile/Treo 600 combo with unlimited internet ($19.99). I just ordered an unlocked Sierra Aircard 860 from ebay.

Now, should I sign up with the new "Total Internet" ($49.99) plan or just use the existing SIM. I will be using it with my laptop on the road (less than 1 hr a day) and weekend (less than 5-6 hours a day).

This card is 3G capable. Will 3G automatically come to me when TMobile goes 3G or do I need to sign up?