There is about nothing on Penrhyn. However, there is telecom and
internet. Flights to Raro are irregular.
I don't think you can clear
customs in Penrhyn. Since you brought it up, has somebody told you that you can? I can always ask the Cook Islanders if you need me to.
If you need provisions,
repair, etc you will have to go to Raro. Don't eat at the chicket hut by the warf! Take a hike up to The Needle in the
interior. Raro has the highest per-capita road fatality rate in the world due to no helmets and drink driving. So if you rent a
motor scooter, make sure you get helmets!
ETA: you should plan to spend some time in Cooks. The people speak
English, are very friendly, prices are low, and the country is beautiful. Telecom &
Internet are far more advanced that FP.