First, welcome to forums as well as the RV world
OK, your question. Keystone, like many, if not most manufacturers really wont have a schematic, or at least one that can be found by us, the ultimate users. To find out if your 8" space will have gas, water or electric runs, your best bet is to open some sort of access that can be easily covered over - a couple big hole saw holes or even a jig sawed hole and a mirror will tell you. Regardless of what you find, there are work arounds such as lengthening wires using junction boxes or rerouting any plumbing feed and drain runs using PEX and ABS tubing. Many of us have found extra storage or made convenience mods - it's just get in and do it mostly, but with a cautious approach that if you see something you aren't comfortable with, you can undo the project and with no outward appearance.
If you are comfortable with your skill level and have a few basic tools - go for it