I've done Anesthesia billing for over 10 years. It looks more complicated than it really is. Granted I haven't done any pain management billing, so I can't speak to that subject, but it's really easy once you get the hang of it.
The ASA Crosswalk is your bible! Essentially every CPT code that allows for anesthesia service is cross-referenced to the appropriate ASA code. Each ASA code has a base unit value. Then you simply add in your variables. For example, the length of time the physician spent with the patient is broken down into 15 minute increments. Each 15 minutes is 1 unit. Then you add associate units for special circumstances or physical status of the patient and add up the total. Then presto! You've done anesthesia billing.
I'm making it sound simplistic, and there are many factors to be considered from proper documentation, (as many carriers, especially Medicaid, require medical records to be submitted along with the claim), the differences between MAC and Conscious sedation, modifiers, diagnosis variables, etc... and as I'm sure has been said, local/state variables which come with experience more than anything.