Hi Steve and welcome to Ukrain forum :)
If you need any advice regarding the West/Central European part of your trip, you might probably be interested in posting this question on the Road Trips forum: tripadvisor.com/ShowForum-g1-i12567-Road_Tri…
Or merely use one of the on-line rout-planners, for example http://www.viamichelin.com/
As for Ukraine, THE only way I insist on you to take if you travel any time soon is E40/M06 Lviv-Kyiv road.
You can read a bit more about it here in the forum. For example, my post #8 here tripadvisor.com/ShowTopic-g777826-i24653-k64… covers part of it. If you have any other questions about it, please, feel free to ask.
As for the customs requirements, please, have a look at these earlier threads:
Reqs to food: tripadvisor.com/ShowTopic-g294473-i3662-k423… (haven’t changed greatly).
Pay attention to the difference between air and land border crossing requirements!
As for the motorhome, I have never had any experience with border crossing in it, so am afraid can not be of any specific help here.
But I’d recommend you to read carefully the requirements to bringing the vehicles into Ukraine (hope you are the owner of the vehicle? Otherwise extra requirements apply to the documents). They have been described great many times on this forum before, and you will find them through search tool.
Don’t forget about the Green card insurance covering Ukraine, because the regular European Union GC does not.
You might also be interested to reading the rare trip reports by those who ventured into driving in Ukraine perhaps? You will find them here: tripadvisor.com/…28348864 (search for road trips).
Feel free to ask if you have any questions not covered by these earlier threads.
Edited: 12:53 pm, May 13, 2013