My girlfriend is in Japan now and we were looking through some sites there and have found some places that sell the TR2/B (similar to TR2AP + bluetooth, not sure though) for about $1,500 or less even for a new one.  I’m half japanese and quite computer literate, so I’m not too concerned about being able to understand the OS and all. 

However, I would say that I am more comfortable in english and I’d like to install my copy of winxp onto it.  But I’d like to know if I’d lose all the Sony OS customizations (which I assume there are) and if so, is there a way to get them back?

It is possible to do but you will run into some difficulties in terms of installing drivers (especially english drivers). Many of the import places like iCube, Dynamism, or Kemplar have successfully installed English OSes on these notebooks with everything working.

You can also check out and search this forum for success stories and tips on how to install your own OS on the system. You just need to understand what you lose in the process. There’s plenty of people here who can answer your questions.