Time for a new/rebuilt engine

I have a 2002 M5 and the mechanic I take it to informs me that I am now living on borrowed time in terms of my engine.Honda HDS It has 220K on it and he tells me that if a rebuild is not done soon a $7K rebuild job could easily turn into a $12K job.
I live in SoCal so I would like to get some info/recommendations as to how much the rebuild should cost me and who in the Los Angeles (or surrounding) area would be best suited for the job. Vagcom 15.7
Thanks for the advice.
GLR