Just did the replacement on our Montana 5th wheel. I used Dyer's RV in Arizona. As stated before they do not want your fabric measurement. Take a photo of the sticker on the roller and have it handy when you talk to the order desk. The supplier will cut the fabric to the proper length for the roller. Our fabric was $206 including shipping directly to the house.
I was able to change the fabric using the Dometic directions found on line. The same directions are included with the awning. Three people are required for the change on a tall RV. I believe you can get by with two on a shorter RV.
Only mistake I made was not pinning the left side roller per directions BEFORE lifting it off the upright. The spring unwound at high speed. Palm of my hand at the base of the thumb was sore for a couple days.