I'm about to start looking for a GC to build a 1/2 bath in a SFH home for me, but this summer/fall I couldn't even find someone to pull a fiberglass bath/shower combo out of another rental and replace it.

Spray foam does cost double what fiberglass does but go figure.

For example are you going to use a fiberglass shower or tile or tub and shower.

My day job as an engineer is making life saving devices for the medical industry (used to do coronary catheters and stents for people suffering heart attacks, currently working on dialysis access for patients with failing kidneys)The lower wall was concrete and steel reinforced, it was constructed of blocks that key together with 1/2" diameter fiberglass pins so that it doesn't shift while being filled with concrete. 

from surface it looks great, do we have to open each drywall, replace the fiberglass and put a new drywall? 

We have done both but prefer a heavy gauge fiberglass surround that we glued to the tile.

I plan to ventilate roof joists and insulate exterior walls with cellulose, and basement floors with fiberglass.- I live out of state so permitting and utility company coordination would be a challenge Thank you all in advance!

We never open these doors because the attic space remains filled with rodent excrement and fiberglass--neither of which we want anywhere in the home, but particularly not the bedrooms.

Can anyone suggest a handyman to help me with patching & repairing a fiberglass shower pan? 

Those that do cover that will want to know the age and construction (they will be looking for newer tanks with fiberglass construction probably).If you are worried about the coverage of a potential removal contractor just ask them to send you a "Certificate of Insurance" which is a snapshot of their limits on their policies that day.