There is nothing comes close to BRAND FFFFF NEW Cadillac.
Its amazing when new, and it age's quiet faster in interiors and other maintenence issues, so i suggest buy cadillac brand new or else dont buy it.
Is second row captain seat come as GCC option in GCC spec model?
If yes then you can source that in spare parts shops in shj at BMW road, much cheaper than dealer price. If its only option in US specs then its tough to source, as in scrap you will hardly get anything for 2008 model, if its older you might get lucky easily.
Get the CKPS Crank position change, often time if everything is fine with engine, spark plug, regular service then main culprit is CKPS for fluctuating (negative) gas mileage.