Use the ATO/CFI to hold maps / pens / etc. when you're entering the circuit or under the hood. They are there as a pax and have hands to hold stuff with, 99% are happy to help.
It's likely that your diversion will involve low flying towards the end and then finding some remote strip you've never seen or heard of before. Don't stress if you can't spot it at first, just run through the local landmarks and make sure you know the towns you were heading for. Once you've spotted it watch out for the engine failure...
CLEAROF or whatever memnonic you use ever 30 minutes is a must.
Don't forget your pre-take-off brief to yourself. "If engine fails before Xkts maintain control, brake, etc, etc.". Or you might find your mixture being pulled just as you throtte up for take-off.
Don't sweat it. You've made it this far and the instructor thinks you can do it so most probably you can!
flog.