Ok Finally finished

Here's my how to guide on changing to an aftermarket single din headunit - on my 99 RS200 Altezza
First like is mentioned you have to determine if you have an amp or not, i didnt have an amp so heres what i needed for the installation.
All parts i bought from ebay for less than £25
1. AUTOLEADS TOYOTA LEXUS IS FASCIA FACIA PANEL FP 25 00
2. LEXUS IS200 ISO HARNESS ADAPTOR
3. CAR RADIO STEREO AERIAL ADAPTER/CONNECTOR (DIN TO ISO)
I assembled the new facia to begin with and clipped in the cage that came with my Alpine stereo, then began stripping the console.
The top section with airvents is clipped in, so tilt the airvents back and get a good grip and pull straight back, with a bit of persuasion it should pop right out..
Click to view attachmentThen pull out the bottom section with A/C and Snow control and disconnect the connector.
Click to view attachmentNow you will be able to see the 4x 10mm bolts, 2 at the top and 2 at the bottom, unscrew these and pull the section out slightly so you can unplug the connections, now the stereo and climate controls will lift out.
Click to view attachmentRemove the climate controls section from the standard stereo, then add it to your new Facia and slide your new stereo into the new facia..
Click to view attachmentConnect the adaptor harness and ariel adaptor to your cars stock wiring connections and connect to your replacement head unit.... Reconnect the climate controls and bolt the centre section back on the centre console... Reconnect your A/C unit and clip back in, and finally clip back in your top air vents and you should have something like this
Click to view attachmentHope this helps

Also see Wozzas
guide on pimping the facia to match the console better... I'll be trying this when i have more time

Good luck