Changing Tiptronic trans fluid

[FHW]

I have a 1998 Base Boxster money pit. Tiptronic transmission is slipping between 4th and 5th gear on hard acceleration. Since I've purchased the car I don't believe the transmission fluid has ever been changed because of other problems I've had with maintenance. I've ordered all the filters and gasket getting ready to change the fluids. Before I started on the change I spoke to a very reliable mechanic who I trust. He told me that the transmission can wear down and get aluminum filings through out the fluid causing some real danger to the transmission failing after it has been changed. We sent a sample of the fluid to be analyzed and it came back saturated in filings. So I'm asking my friends what options do I have? Change the fluid risking failure, Purchase a rebuild, Drive it until it fails on its own?