Mast support
I'm not familiar with the setup on an E23, but I had a 23' trailerable sailboat where the mast was very easy to remove and reinstall with two people. I think on a boat that size, I would be more comfortable removing the mast, than risking a bump that dislodges the 2x4 support while removing and reinstalling a bulkhead.
It is also important to remember that at least one side of the stays will be disconnected while replacing the bulkhead, possibly resulting in the mast tipping. Have you talked to a marina to see how much it would be to pull the mast? A good lift would have it off in minutes.
I did the bulkhead on my E32 without removing the mast, but I also did not replace the entire bulkhead. I wanted to replace the whole bulkhead, but due to time constraints and $, I only repaired the offending section, leaving the mast support alone. One of the biggest challenges was what to do with the stay connected to the chainplate.
http://www.ericsonyachts.org/infoexchange/entry.php?176-Ericson-32-Bullkhead-Repair I made a few different blog entries, some with photos.
Good Luck! Please let us know how you do.
-Dean