How to set desktop up for using WiFi

You should have no problem using a wireless 802.11G PCI card.
It will insure backward compatability with older networks.

I would suggest you have someone install an external wireless antenna
to make sure your signal isn't blocked by the metal skin of the RV.

You will also need to make sure you have a power inverter that has a high
enough output to handle the computer and monitor unless you plan on
strcktly operating it from the generator.

So, all I would have to do is to install one of those cards in one of the slots in the back of the computer? Right?

I would be hooked up to shore power, like at campgrounds. I only want to use this with certain campgrounds that offer free WiFi when we happen to be on the road traveling. Would I need an inverter for that? I thought inverters for using when not hooked up to shore power? Not sure now that you mentioned what you did.

What kind of internal wireless antenna would I be needing and how hard would it be to hook up? Are there external wireless antennas that one can use?

GQ

Just install the PCI card and the software.
It will come with instructions.

Yes there are external antenas available.
You just unscrew the antenna from the back of the PCI card
and screw in the cable from the external antenna.
Since your only going to use it at campgrounds,you don't need to have it mounted,
although it would be less hassle if you did.
You could just put it out the window or door.
If your just using shore power,you don't need to woory about an inverter
to convert 12VDC to 120 VAC.