I'd suggest contacting a personal injury attorney asap. You may, or may not, have medical payment coverage on your vehicle insurance which should help pay for medical bills right away to help you avoid bad debt. Inevitably, the other driver (or his insurance carrier) should be responsible for paying for your pain and suffering as well as medical bills.
If the party was in Greene County, the officer may be referring to a letter allowing you to go through a diversion class (it's an 8 hour class offered on Saturdays) to avoid being prosecuted. Whether the course is offered or not is up to the prosecuting attorney's office and if the class is not offered (or you decide not to attend), the prosecutor may still file charges. I would be glad to talk with you further if you'd like. 417-720-1098.
Without more details, I can't say for certain why you need it but $2,000 is more than the IID should cost you. My guess is that this is your second DWI conviction. If that's the case, then it's required. You can call the Missouri Department of Revenue for more details.
Good points made by the attorneys that have answered this question so far. I would simply add that in Missouri there is a statute that can sometimes be used to reduce medical liens. You should contact a local personal injury attorney.