I would not go down the route of removing the fretboard etc - the bass just isn't worth that time and work. The non-Japanese versions come up on Ebay regularly and don't fetch much sadly.
There are other ways to release a jammed trussrod though - I've been there. It may be jammed as there's too much pressure on it from the bend in the neck and/or the strings being at tension. What is the profile of the neck as it is now, does it have a front or back bow?