After much hesitation (lasting several weeks - debating should we or shouldn't we) we finally bought our car from Dubai Star in the Automarket in Ras Al Khor and I have to say received very good customer service, they arranged our car insurance, salik tag, car service etc, overall it was very good value. I am also pleased to say the car is still running very well.
I bought my Pajero through Al Futtaim, I got them to put me on a waiting list for one and they called me when they had one available. Got a great deal on it, with warranty etc etc. It is worth it with them to be honest as they're very good.
As fjcruiser says be very wary of the market lots of dodgy dealers there. You could try Mitsubishi themselves and ask them to let you know if they have any trade-ins.
Be careful with the Auto Market: loads imports, accident-repaired and all sort of dodgy stuff around. Look at Park and Shop adds. Many expats advertise their cars there. Good private deals also on Dubizzle. Have a look at Philippine Car (you can google their name). A friend of mine advertised his tip-top Pajero 2005 on Dubizzle privately and got the price he wanted from Phillipine Cars. He had in fact had bought the car from them 3 years before.The guys were very good, did all the paperwork at his home.
Good luck. Buying privately is fraught with risks but is possible (took me 6 months to buy the car i wanted!), you will get some warranty from a dealer but personally I would stay away from the Auto market.