For a first trip, contact a company like Skyplan, Jeppesen or Colt. They can help sort out any of the initial flight planning questions as well as help with making sure the ATC filings have passed the Eurocontrol muster and ensure they are filed in a timely manner with the appropriate slots. They will also know enough to ask the appropriate questions regarding HF, MNPS, etc to ensure you're able to legally do the trip. Being refused your oceanic clearance is a bad time to find out you can't fly the routing you want due to lack of proper NAV equipment.
The hint about making sure your passengers recognize the importance of being on time is VERY important, unless your passengers like to sit for several hours on the ground in their airplane missing their next meeting in the next city. Some European airports are incredibly easy to get in and out of, others are a pain in the a$$ and a good ground handler is essential.
After the first trip, should be pretty easy for any professional flight crew to handle, give the North Atlantic charts a quick check and go for it.
amraam