If you have the skills, all of the work can be done without too much difficulty. As you found out, you can get the materials to completely replace the roof for 10% of what the dealer will charge you. Building the cabinets yourself will be almost the same thing with the total savings of thousands.
In all probability, when everything is done, you will be lucky if you break even on this coach, which is MUCH better than most of us do financially that own RV's. Just looking at the coaches owned by some of the naysayers about rebuilding this coach, the depreciation loss alone each year on their coaches is more than what it will cost you to rebuild this one.
You don't get in to RVing to make money. It is all about the adventure and enjoyment.
Have fun with the project and set small goals that you can accomplish in a short period of time. before long it will be completed, paid for, and you will be enjoying the fruits of your labor. IN addition you will learn skills that will help you if you ever decide to upgrade.