This is for an E36 but the pics of how to remove the chip are the same for the E30 (figures 7-10)
The DME for E30's (at least my car anyways) is located in the glove box. You have to remove the upper plastic pannel to get at it. Also you probably won't have any torx screws that need to be removed (my DME only had tabs that needed to be bent up to remove the cover)
just follow the pelican E30 chip replacement article http://www.pelicanparts.com/bmw/tech...ip_install.htm
and use the other link I posted for reference when replacing the chip.