We just purchased a Ford Transit 350 HD with a 12 foot fiberglass work box on the back.

It's not your standard fiberglass shower. 

The following items are covered under building coverage as long as they are connected to a power source and/or installed in their functioning location:Sump pumpsWell water tanks and pumps, cisterns and the water in themOil tanks and the oil in them, natural gas tanks and the gas in themPumps and/or tanks used in conjunction with solar energyFurnaces, hot water heaters, air conditioners and heat pumpsElectrical junction and circuit breaker boxes and required utility connectionsFoundation elementsStairways, staircases, elevators and dumbwaitersUnpainted dry wall and ceilings, including fiberglass insulationCleanupThe following items are covered under contents coverage:Clothes washers and dryersFood freezers and the food in themFlood insurance does not cover basement improvements or items not necessary to make the home safe, sanitary and functional -- such as carpeting, finished walls, paint, floors, ceilings, furniture or personal belongings that may be kept in the basement.

Our houses are Ballon framed houses from the 40s, where fiberglass insulation was shoved onto the sill plate.

@Jim K.I have been lucky picking up special order returned (SOR) fiberglass tubs from Lowes.

One of the apartments in the 6-unit building has a cracked fiberglass bathtub.

Put in new electric, fiberglass insulation and remove the garage door. 

I have read poor reviews on the Lowe's fiberglass tubs cracking, saw a youtube video of a review on a tub that had 4 solid feet on the bottom to keep it from flexing\cracking but can't find the video again? 

Install rockwool or fiberglass insulation rated for sound between the joists.

My wife has also used spray on oven cleaner in really soap scummy showers and it works wonders at cleaning up a fiberglass shower, so I imagine a sink it would work well too.