Yesterday, at our sword club meeting, another collector and I put out mokume tsuba. One tsuba that he had was basically the same as my tsuba. The only significant difference was that mine was signed and his was not. Synchronicity???
The wait list for fully trained polishers in North America is long. Sending to Japan could be quicker especially if you will be sending the blade to shinsa.
Your sword would not be confiscated. They do not do that. 100 years for a sword is quite young. You would need an agent to take care of importing the sword into Japan and arranging for export of the blade after the work is done. Usually when sword is polished it also probably needs a new habaki and a shirasaya. Many are submitted for papers before the blade is returned to you. Every part of the process costs money. The yen has gone down considerably so now is probably a great time to get work done.
Welcome J you will find quite a few martial arts guys here. Tom who just replied to your post is one of them - me too. There is a lot to learn; the search function will help you find information on many topics.