You are going to want to have the shore power house connection ready for him to hook-up, if you haven't already done it. Proper receptacle- 30 amp, etc.
You will need a switch to transfer the electricity from shore to genny, although some just swap plugs. So you will need a manual or automatic transfer switch.
You mentioned fututre solar plans, so have the wiring you need ready for him to rough-in for future solar install. Buy batteries last-minute to ensure freshness. Panels will only get better/cheaper with time. You will also ultimately need a controller.
Have plenty of ladders, light and a clean workspace to make his job easier. Mark with blue painters tape where you want outlets, don't forget one underneath vehicle for batt charger, engine heater etc.
Have lighting fixtures ready- are you also installing 12V lighting to compliment solar setup?