I've been doing ambulance billing for about 20 years and I must says it has gotten a bit easier in the last few years. The procdure codes are pretty much standard across all of the payers. The local coding gone at least in Pennsylvania where I work. Some payers still want copies of ambulance patient care reports but those are dwindling. PMNC's for Medicare non-emergency ambulance claims are annoying especially if they're not filled out properly.
Documentation is extremely important. EMT's and Paramedics have varying degrees of charting desire. Some times the billing signatures are missing. All in all I would say it's not too bad.

Russ