Had to replace a dead WAP with this 1262 the other day, but the replacement had an automous config which need to be converted to lightweight for it to talk to WLC.

The WAP got an ip from DHCP which I needed to telnet to it later. (Otherwise would need a console cable)
Setup a tftp server (SolarWinds), which will serve the tar file.

Use putty, telnet to the WAP (u: cisco, p: Cisco)

ap> Enable
ap# archive download-sw tftp://<tftp-ip>/ap3g1-rcvk9w8-tar.124-23c.JA.tar
ap# wr mem
ap# reload