Learn to Setup C1801 and 1142n

Sure. I recommend reading the Cisco installation docs, and following along. Their documentation is pretty decent, the intro stuff does walk you through the basics pretty quickly and efficiently.

The router generally you'll be expected to do command line access on it with a serial port, so make sure you have a working serial port/USB dongle first and console cable.

Go through the motions of setting a simple IP address on an interface with the Quickstart guide.

The 1142 quickstart guides generally refer you to the web GUI on the box. It may just be me, but I feel the CLI is still much easier on the AP than the GUI, but the docs for the CLI of the 1142 aren't as good.

You need RADIUS in order to do enterprise level authentication, or if you are doing a more advanced security model with 802.1x and certificates and such. Cisco has both a built-in RADIUS server for authentication on the 1142, as well as the option to use an external one. Or you can forgo that altogether and just use pre-share-key (PSK). Cisco does de-emphasize PSK quite a bit for their WiFi stuff, but it can be done.

Start with the Quickstart guide, and the installation manual in the Cisco docs. I'd point you to some URL's, but Cisco.com seems to be down today right now. Sigh.

Console in and 'write erase' and reboot. Or do you need to do password recovery?

Once you have some basics on your routers, be aware that you can now emulate a whole network of cisco routers on your PC.

Dynamips.

It runs real cisco code so you need to have access to real cisco software images. Someone with a clue might be able to find some on t'interwebby.

I might eventually read emails sent to me on this junk account.