In the case that the original 1997 transmission control unit doesn't work, the module from the 2002 will work. Simply remove and unplug the old unit, install the new '02 unit in it's place. The
986 USA Katalog shows that the modules previous to 2000 are not forward compatible, but the 2002 can be used in all earlier models.
From Illustration 901-03 from the "Main Group 9: Electrical Equipment" section:
I expect that the 1997 TCU will be functional, but not optimal.
Disclaimer: Markus usually knows what he is talking about, and I'm just reading from the manual.