I can't think of any repair I've done that is as difficult as you have descibed. I guess my most difficult have been removing engineered glued down to plywood subfloors and patching back in. Ya know, the icemaker leaking under the frig routine. The flooring comes up in little chunks and takes some of the plywood subfloor with it. Then scaping and chiseling off the glue and bits of flooring and repairing the subfloor to allow one to reglue new flooring to it. Then weaving in the new while trying to keep the T&G's intack and not sliding the wood in the glue. Damn near impossible feat to do well. When I see these, I want to recommend full replacement!