Just 2 straight runs? no valley's where a porch ties on or anything? If you are gonna do it yourself, the materials will probably be in the $2000.00-$2200.00 neighborhood.
Dont forget the powerhead, plumbing vents, fart fans, furnace vent, etc. On most mobile homes, they will all be on one side. I recommend a fresh layer of felt paper too.
They likely used something that looks like plain brown paper with an extremely thin (sprayed on) layer of tar between the brown paper layers at the manufacturing facility.

I bought mine from Nichols metals in the Boaz/Albertville industrial park last April.