"Will the wireless pc card adapters on the market work on this computer?"
I'm sure one of them will. There were some issues with some cards, but most of that seems to be some 0.01% issue and it's unlikely you will get that one.
"Do I have to add anything else besides a wireless adapter?"
A wireless access point to connect to. It's noted in the linksys website about such setups so I don't duplicate web content in this small space.
Bob
I have a Toshiba Satellite 4000cds/cdt series laptop
and would like to set it up to be wireless. It is running Windows 98 and has two pc slots. Will the wireless pc card adapters on the market work on this computer?
Do I have to add anything else besides a wireless adapter?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic