I attached a link to a video demonstration from Mojo Musical Supply that might give you some useful ideas. Here they’re replacing the entire controls circuit in a 335 workin through the f-hole. They use string tied to the threads of the the components and then fish out the strings to get the components in place. The same technique would work for all kinds of hard to reach installations.

http://www.mojomusicalsupply.com/video-335.asp