Sallie Mae Wage Garnishment ??? DO I let it happen?

I'm about 60 days past due with Sallie Mae on a 125K FFELP consolidated loan. The payments would be about 850/mo. Right now, I owe 1700 past due and another 850 by 11-28-09. I am trying to decide whether to let the loan go into default and have them garnish my check or take out a loan to get current and apply for an income-sensitive repayment plan which would put my payments around 600/mo (which I can probably handle). If I let it go to garnishment, the garnishment will be about 600/mo. I don't know how much time I have to figure this out. How soon will they garnish my wages? I heard 270 days were required to pass before you are in default, and then they have to send a 30 day notice. Is this correct? Also, can they garnish my wages at 15% AND attach my checking account? If we do enter into garnishment, and then our income increases (not mine, but my husbands--he's NOT on the loan), and we are able to make the payments, can we request to stop the garnishments and make the larger required payments? Or, are we garnished forever? Sorry about all the questions, but I'm really not sure what to do...