Changing missions to another scenery can be a little tricky and requires some work, yes.
When I do it, I first hand-edit the entry of the airbases file for the new scenery airfield into the mis file of the mission I want to update.
That way I was able to avoid the CTD problem when starting the mission in MB. Then of course you have to adapt the layouts etc.
Considering how nice UncleTgt's new Solomons scenery is it would be a shame not to use it, in my opinion.