Just purchased a used 1973 Hi -Lo and love it. There are a few things I need help with. A manual would be a big help. I have to hook up the toilet and sink.

Sorry but I don't think you will find that information in the manual. Nothing like that in the newer manuals.

Where can I find more written info on my HiLo. I am finding fuse boxes, switches etc and need some giudence

The fuse box information should be in the manual, switches may or may not be. Do to the age things may have been changed. I changed several things in our 1995. Post some pics. of switches, maybe someone will know what they are, as many years were similar. You didn't say what model or length?