Hello advsysco
The slot you are describing is a VRAM (Video Ram) slot. The slot under the metal cover is the RAM slot (144-pin, 100 MHz or faster SO-DIMM).
You can purchase 4MB SGRAM SO-DIMM chips to raise the Video RAM from 2MB to a total of 6MB. The Apple service part # is 661-2023. You can find them on the web or I just saw a few on eBay.
David.
http://www.UsedMacs.us