I'm pretty sure Roddoors is back in business, 'cuz they have a web site under that name. They still offer your headliner kit. I was confused by the three piece thing, but the main headliner is just one large piece, which makes sense.
You will need to put something in between the headliner and the roof to keep it from banging together and driving you crazy on the road.
Get some really good high heat resistant top and trim contact adhesive like DAP or 3-M, and NOT in aerosol cans. You don't have to spray it, you can roll it or brush it on, but spraying would be the best way to apply it. I would glue the headliner material and the headliner panel only in the middle at first. Leave a band around the outside edge of the panel about 6 inches wide that has no glue. Then attach them together and let that sit until it's completely dry. Then go back and do the outside edge to finish it off. You will be surprised how much the material will stretch into the rear corners.
No one lives forever, the trick is creating something that will.