Most of the information that you want will be in the Irish AIP.
You can register free with Eurocontrol
, select 'enter applications', then 'PAMS light AIP'.
Search Ireland/AIP/GEN for general entry requirements and the AD section to find if customs are available at your preferred airport.
You can save money in Iceland by using Akureyri or Egillstadir as they don't require a handling agent. Isafjordur is also available with prior permission.
Weston and Donegal have customs available with 24 hours prior notice.
You'll also need liability insurance to EC/785 minimum and permission from each country to use an amateur built aircraft. That costs about $400 from Greenland and $150 from Iceland IIRC; not sure about Ireland.
You can rent dry suits and liferafts at Goose Bay either one way to Wick or drop off on your return.
It's a great trip
to do. Make sure you take in some sight seeing!