Medical Debt Collector

Being sued by a debt collector for some old medical bills in Montana. We filed an answer to the summons and had a mediation date scheduled. The debt collector filed to reschedule because they were unavailable that day. Now we’ve received a packet from them as a Request for Discovery asking for all of our personal information and admitting to each “Exhibit of debt”. The letter is dated 12/10 and says we have 20 days from date of letter to provide all the information. I am fully prepared to go to the mediation and settle upon a payment. I was not told I would need to do anything before the mediation and I do not feel comfortable sending this company all of my personal information along with my tax returns and pay stubs. Are we legally required to provide this information before the mediation? Obviously never gone through this before and have no idea what to do!