Check here. It will take you through the whole process. The transmission shown is in an E36, but it is the same transmission as yours.

I bought a laser temperature gun at Autozone for about $29 or so. I shoot the transmission pan to get an idea of the fluid temperature.

Hope this helps.

__________________
Steve

Calypso Red 1992 525i with 170K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold