After you have sprayed that and let sit then you can either sand or just paint.

Then I sprayed the stain myself ($100 for gray stain that mixes w water and a $100 on a high quality pump so it doesn't drip).

He wants to have a professional come out and spray.

@Wendy Vaidic,If you install a shower, I would suggest that you include a "body spray."

I would spray 2.5" minimum in the stud cavity to meet the 2012 energy code of R-13 in walls. 

Would spray some weed killer down and have some churn the soil so it's dirt, Maybe lay some stones down and make a stone fire pit?

They come once a quarter no matter what to do some maintenance (spray exterior etc) but you can call if anything else is needed. 

Milind,Yes, your solution will work and is the right way to do the repair, just make sure you seal all the threads real good and test the joints with spray to make sure no gas is leaking out of them. you may want to test as many of the old joints that you can as well, just to make sure no gas is leaking out of them.

Get a gun, get a taser, get pepper spray.

What we did though was new tile on the wall, sprayed the tub white, did LVP flooring and installed a white shaker style double vanity.