WELCOME!
I've got a 2001 TD5 XS.
Do a search for the 3 amigos. Incidentally a wobbly wheel bearing can also throw up the ABS light I believe. Sadly, if a wheel bearing has begun to wear out then Land Rover, in their infinite wisdom decreed that Disco 2s have to have complete new hubs which contain the bearing. (I'm sure there's an actual repair out there on the t'interweb, but I for one will no doubt buy a new hub when the time comes).
The reason all three lights come on is that hill descent uses the ABS sensors to detect wheel locking (it doesn't want locked wheels!), traction control uses abs sensors to detect wheelspin and brakes the wheel to enable power transfer to other wheels. There's no centre diff lock on the earlier series 2 Discos like yours and mine, so once a wheel spins up we're going nowhere without TC. However, the spigot should still be in the transfer box and you can or could get a kit to modify the transfer box lever so it was as the series 1 Discos.
Diff.