I bought a 1990 LS 400 a month ago. The theft deterrent system does work. The light doesn't come on. I check the fuses, seem to be alright. Any ideas?

Also idles high in the mornings or if its been sitting for a while. Around 1600 RPM and when warms up come down to like 600 RPM. Lexus says it needs idle speed control motor at $900 parts and labor. . I've search all over the net but doesn't seem to be such a thing as a control motor. There is control valve though. Anyone knows anything about this? Where is it located?

Also, temperature gauge comes on erratically, it would be down for a while then would just start working. Don't want to get instrument cluster re-done just because of temperature gauge. Any ideas on how to solve this problem?