When I install MIUI, I flash Gapps, and I get an icon I can open. You could try that. It should be safe to flash at any time, but it may downgrade other gapps you have. You would be able to just update them via the market, though, so no big deal, IMO.
You can long press any homescreen, add a shortcut to "activity" car home.
and... from xda:
Car home contains two components, the activity (this is the app we're updating) and the launcher. The activity contains the guts of the program, but the Launcher allows it to show up in the app drawer.
If you're using CM6, you have CarHomeLauncher.apk already in system/app and just need to install the com.google.android.carhome-1.apk file. If you are not using CM6, then you may need to install both the Launcher and the carhome apk if the carhome app doesn't show up in the app drawer.