The fret board may need to be leveled and not replaced. Some neck mechanics replace only a portion of the board. In any case this is a pricey job. Figure a couple hundred dollars just for the re-fret job.
Then add the labor(labour for you Brits) and materials for the new finger board. Is the old Montoya worth that kind of expense? Sentiment and the perfect fit may say yes for you, no to some others.

Good luck but have a pro look it over.

Don