1) Well, it appears that the solution will involve building a converter box that has two processors running at different crystal frequencies, with either a SPI or parallel interface between them.

2) I would like to look into the possibility of using the USB port instead of the COM port.
1) That is silly, use a two UART '51 chip, there are several of them available see http://www.keil.com/dd/parm_search.asp

2) possibly a very good idea, check appnotes etc at Cypress.

Erik