hooked up my iPod to my McIntosh today! took me 30mins! now i can control my ipod thru the OEM headunit!
all u need is a "Clarion CeNET iPod interface" unit which can be had for $200 from the shop or there is a guy on ebay selling them for $170(dont know about warranty issues etc etc). The model number is EA 1251. Then its jsut a matter of taking out the McIntosh and plugging in the CeNet cable into the back of the headunit.
Ill take some pics soon and post them up. Theres not much to see because everything is hidden, but u can see where i put the ipod and how OEM it all looks!

not sure if this is the same for the normal headunits in other Liberty's but if you have the CeNet slot at the back i cant see why it wont work.
Also, the unit also charges ur ipod!