Problems fitting double-din stereo to 2.5

[gd49]

Decided to replace my OEM stereo (in a 2003 Nevada) with a JVC KW-XG701, a double-din stereo. I've fitted it, and it's working fine, but it seems to jut out slightly from the console. It came in a sleeve, so I took the stereo out of the sleeve, put the sleeve in the dashboard, then slid the stereo into the sleeve and screwed the radio into the sleeve, was this correct? The stereo didn't slide in quite as far as I expected, compared to the OEM stereo. There were instructions with the radio for removing the retaining clips from the OEM stereo and attaching them to the new radio, do I need to do this instead?

I'm using the ISO wiring harness adapter from mx5parts.co.uk, this seemed to be quite a chunky piece of kit, could it be stopping the stereo sliding in fully? There's also a metal bar at the back of the cavity for the stereo, will this stop non-OEM radios sliding in fully?

My check engine light has also come on, tho the car's running fine. I suspect it's related to when the alternator belt snapped, but could it be triggered by incorrectly fitting the radio?

The radio
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItemVer...
Cheers for any advice