The '90/91's aren't super rare yet. Are yours damaged? Should be a whole lot cheaper/easier to find ones in better shape. Really should be no wear to them.
LED's aren't going to happen without a bit of work. If you aren't the type to adjust the dimmer for gauges, then there are ways to make them a bit easier to use, but for reliability, you are going to have to replace the cluster circuit "board", and replace the instrument panel connector. Basically, use wires and connectors vs. what GM did.
You can get $5 12V PWM dimmers off ebay, and either "hard wire" them for one brightness, or you can remote mount the dimmer wherever you want. IMO, this is an all or nothing endeavor...hardwire everything, or don't waste your time.
The issue with LED's is that they don't dim properly just by changing voltage, which is what the headlight switch does. Now, find an easy and cheap way to incorporate a PWM dimmer into the stock headlight switch, and I'm all ears.
You can find my thread on cluster hardwiring for an idea of how much effort it takes.
Here's the link BTW:
http://coloradok5.com/forums/showthread.php?t=304941&highlight=hard+wiring+cluster
