As has been mentioned above contact Fleetwood and they can probably send you a PDF on the plumbing. When I purchased our used 98 Pace Arrow last fall I contacted them and received them immediately (great customer service). I would imagine that they would probably still have yours; I also asked for and received the electrical and hydraulics schematics as well.
I too would replace the lines with PEX tubing. This route may cost a little more iniatially (as you will have to purchase the crimping tool) but in the long run you will be better off and it will be much easier to repair the water lines in the future if need be. Now getting to your lines, etc. is a totally different challenge, I've looked at mine and I'm not sure where or how I'd get to some of the lines and I really don't want to find out either.
Good luck with your project and keep us posted on any updates.
Ken in Nebraska
98 Fleetwood Pace Arrow, 35U
97 Ford F53 chassis