If puppy has Network Manager (and probably does) you won't need to do anything if the adapter you buy has drivers for linux (at most it won't charge them automatically and you'll have to make the machine do it editing a file ;) )

Have a look at this forums, this has been asked before (for a usb wireless adapter ) :)

I agree with Marc, getting it to work should be quite easy if the adapter has native Linux drivers. Since it sounds like you haven't already bought an adapter, you should check out this list of USB wireless adapters with native drivers:
http://wireless.kernel.org/en/users/Devices/USB

bllueskull wrote:

how hard is it to do the editing? where can i get the software for it?

If you buy one of the adapters from the list I linked to above, it should be straight-forward to determine what driver and firmware to use. You would then have to install these, and use a text editor to add one word to the file /etc/modules. The network settings should then be configurable graphically.