I just did the same thing. I found that the vinyl over the wood areas was not firmly attached so I removed it and then primed the wood with acrylic wall paper primer. The areas where the vinyl is on aluminum was still firmly connected, so I just left it in place and cleaned it thoroughly before putting up the new wallpaper. I used self-adhesive wallpaper from Home Depot.
1994 Excella 25 Follow the build on Gertie!
1999 Suburban LS 2500 w/7.4L V8
1974 GMC 4108a - Custom Coach Land Cruiser