While it is difficult to find doctors out of state to agree with the reporting requirements of calif WC, they are not subject to the Calif fee schedule...but that still doesn't make it any easier.
The thing to keep in mind, as you say you are retireing soon... IF you are Medicare eligible within 30 months...through age, disability or application (for SSDI) you must take Medicare interests into consideration when there is any type of settlement to your claim. Particurlarly where you entitlement to future medical is affected.
There are some new laws going into affect next year that makes this even more important.
IF there is an issue to Medicare... you must submit a WCMSA to CMS/Medicare and they will tell you IF your need a setaside account and HOW MUCH will be required to satisfy CMS.
As to your question on 'how much money?"
There is no way to even guess to that.. one, you don't provided enough information... and two, more importantly... there is no way to tell what an IC will do when it comes to a SWAG..or "Scientific Wild Ass Guess"...(an accepted term at many WCAB offices these days)
FM is always up in the air...and usually paid in "todays dollars'', and never enough to begin to cover any treatment you may require...