I operated from Chezh Republic earlier this year. Bring a copy of CEPT document (it contains reciprocal information in three languages ) , your FCC license and obviously your passport. Also search frequency charts applicable to those countries. Print it out and bring with you.
I believe CEPT agreement gives full privileges too US extra class licensees. There may be restrictions if you are a general. Technician license holders are not eligible. Read about it.
I brought my FT817D with me but wished I brought my ft857 instead. The only antenna I could practically use was a BiddiStick. In Europe they dont build buildings out of sticks and plywood like in the US. Everything is brick and concrete with rebar. Operating from a hotel room is not going to be easy. I was lucky to have a balcony where I mounted the antenna. Buddipole was marginally better than a dummy load and it was a pure pain to tune properly. I had to use my MFJ Travel tuner to bring SWR to acceptable levels. An End-fed antenna would have been a much better choice but I had no where to hang it.
MFJ Mighty Lite 25 A power supply would be your best choice. It accepts both 120 and 230 VAC but you will need a plug adapter. I suggest to buy at least 3 adapters because you'll need them to run your radio and charge your phone, computer etc. European to American adapters can be found on ebay. I bought a pack of 6 for a few bucks.
I strongly suggest to find a local club in the area you are going to visit. They will most likely let you operate their club or personal station. I had a very warm welcome from Chezh hams. They let me operate from their club's contest station. Language was a bit of an issue. I dont speak Chezh. We used a mixture of English and Russian to communicate. A few guys spoke German too. No problem.
Having a 4 square, 8 element each array on 20,15 and 10 meters was nice. And they had an Acom legal limit amp to supplement the antennas. I had a blast handling a pileup of American stations calling me. I turned the antenna East and there was a pileup of russians calling.