Old Gateway - support, bios, WiFi

Recently acquired an old (2003) MFATXPNT ES2 300X CEL. Basically an older Gateway desktop that uses a Intel motherboard: D845GERG3. This appears to be a Gateway/Intel motherboard, and as such it seems that there is no longer any BIOS support from Gateway ... kind of frustrating, yes I know it's old but a serial number entered on their support site basically says there is no such animal; at least say "it's old, we are no longer willing to help you" or something.

So, I have loaded Linux Lubuntu on it as the xp was trashed, which runs, but is slow; one major issue is only 256K memory (RAM). This old memory is cheap, would like to put in at least a Gb but how can i tell if it will be supported by the existing bios: RG84510A.15A.0037.P15.0304012013 (have not had any luck searching as yet).

The processor in place is a Celeron 2.4 GHz.

It would also be much more convenient to have a wireless card in this, but not sure what to buy. Tons of PCI wireless cards on eBay but not sure what would work with this old system...

Similar situation with Graphics card (what would work). I know already ...

1) Not really worth the trouble (kind of a hobby and learning more about Linux).
2) I know I can't/don't want to run the latest greatest. If I can get a wireless card for a few bucks and a graphics card (relatively old) for a few bucks and throw in some more memory and get it working I'm happy.

Chris