Garnishment on medical bill/no insurance

I have had a lawyer after me for about a year for a anesthesia bill for a surgery done in 8/97. I had origanally set a payment of $20 a month but accidentally forgot an called the next day to let them know that I would bring it in the following Monday. The next day I was served court papers and like an idiot I didn't do anything about it. Now they have called me and said they have a judgement against me and that they are going to garnish our wages. I am only working a part time temp. job right now and my husband is not working but collecting unemployment while he is looking for work. My first question is..Is there anyway that I can get this bill written off since I didn't have a choice on the service and didn't have insurance at the time? If not, how much can they garnish? We are having enough trouble making ends meet. Any advice or help would be greatly appreciated. I live in Utah.