I was using mine as an ap for some time, before I got a real ap. It did an alright job, not sure if there was a speed hit or not.
Anyway, first you need the right kernel, either 2.4.20 or 2.4.21
If you're not already running it, it's the kernel in red hat 9, or compile it yourself. There's plenty of howto's on compiling kernels, just start at google.
Then get the rtl8180 package
Once that's unpacked, look at the Makefile, there will be a section where there's two lines, one commented out, for whether it runs in infra/adhoc mode or in ap more, make sure the ap one is the one not commented. compile it, ie make && make install
install the module, modprobe rtl8180_24x
hopefully it'll work alright, it always did for me.
then look at the wlanup and wlandown scripts, and the descriptions of commands in the readme, should be able to work out how they run.