I'm glad you like it :D
Installing room upgrades is done by viewing a maid carrying upgrade materials and selecting "Upgrade Room" or by having a maid interact with upgrade materials (maid -> materials drag+drop; should show as "Upgrade Room" as well).
A pdf manual is a good idea; I probably won't get to it until the game is nearing full release however as the manual is still a work in progress (there's some sections that need updates currently actually).