The attorney does need a court order to garnish your wages. That would require a bit of time, but not much. If this is an experienced collection attorney, he could have that order in less than 45 days. Your employer could begin garnishing wages in less than two months from the date of this letter.
This type of judgment is good for 10 years from the date the court originally signed the order. At the end of the 10-year period, the creditor can renew the judgment through a very simple process for another 10 years, and so on. You could have this judgment follow you for decades.
You have a little bit of room to negotiate because in most cases, the creditor's attorney would rather be paid a lump-sum amount to settle the case rather than receive monthly payments from your paycheck. He or she knows that while an employer can't fire you for having this garnishment, the employer could find other convenient reasons to dismiss you once the garnishment begins.
Employers don't like employees in financial distress. They are distracted and, some people believe, are more inclined to take shortcuts because of their financial issues. Law enforcement is particularly averse to hiring someone in financial distress because the employee dealing with financial issues is more likely to take bribes in order to resolve their problems.
You have a couple of options. The best one for your credit is to pay the debt. If eligible, you can file bankruptcy to eliminate the judgment and balance. Or you can also try to settle the account with a lump-sum payment or short-term repayment of a settlement.
However, the process you currently have taken -- head in the sand, hope it goes away -- has finally caught up with you. Don't wait any longer.