If you can't get a single fiberglass unit in the opening I would recommend getting a shower base and tiling the walls. 

Two of my rehabs only had some old fiberglass insulation that was less than the height of the 2x4 and another one had nothing.

Should I go for metal or fiberglass?

I put up vapor barrier, fiberglass insulation and drywalled.

Turns out the door was fiberglass and was all frayed outside from the animal hitting the door.

Is this a fiberglass shower?

I'm guessing a prefab fiberglass replacement of sorts??

I've already made several improvements to the property including new gutters, french drainage system, some moderate plumbing work (shut off valve installation), repair and resealed asphalt parking area, and updated the units kitchen and bathroom I'm living in.I'm considering installing insulation in the building via blown in cellulose/fiberglass, new windows for building, and new landscaping (currently there is none).

Cost $500 material + $100 labor No Glue Vinyl Flooring with Fiberglass backing (Kitchen,Dining, Bathroom) cost $800 Install + Material.Paid 350 Labor to install 3 Ceiling Fans, 5 Light fixtures, and change out all the plumbing fixtures in bathroom and kitchen.

Cesar's suggestion is a good one for many markets, I am a little concerned about doing a fiberglass surround system in Rye.