Just did these in my car a couple weeks ago. In case you don't know already, the dimmer on Omori gauges works differently than Subaru's dimmer. You either have to set them up for constant brightness, or there is a circuit you can build
here so that they will work with your dimmer.
The circuit is not hard to build as long as you can use a soldering iron, and the parts cost about $5. Mine works great, and the gauges are awesome.
Good luck, not a hard install, but it does take a while.