Running OSX with 128MB ram gives you a slow performance since OXS needs more ram to work adequately. I would max the ram to 1GB (2 X 512MB PC 133 sodimm ram), replace the 12GB 4200 rpm hard drive with a IDE 2.5" 5400 or 7200 RPM hard drive and install Tiger 10.4.11 or Panther 10.3.9.
There's a 500MHz G4 processor upgrade for the Pismo. You may search the web via Google to find it. Concerning the wireless I would go for the Apple Airport Card first generation ($30 to $40) since the Pismo internal antenna has a good reception.
The Pismo was one of the best Apple laptop but unfortunately it has only 8MB video ram and that's not enough for actual internet use so no youtube or video streaming.