Well - I havn't done it yet and my cars not ricey - just a show car.
Problem with our cars is the akward rear panel which makes it impossible for a kit job. I have having custom hinges made for my rear doors. I already have a custom front lambo set up.
As far as that $300 figure - not sure where it's from. My lambos come in at about $2000 after everything. The rears will be about the same since they require a lot fabrication but less moving parts.
The Contour will probably require a recessed hinge setup with shocks in the cpillar area. I'm not sure but I've seen a PT Crusier with the rear suicides and he had the same problem that we would encounter.
Once I develop the kit I can prob send you the CAD version at a price. Regardless, your best bet is to go to a lowrider shop or hotrod shop. Those guys know what they're doing. My lambo doors were done wrong by the first shop that did them but the second shop did an extremly awesome job.
Biggest problem besides designing the hinge itself is lining up the doors - some shops like the afore mentioned one just wanted to get the door on there and didn't take the time to line it up or do the proper fabrication on the hinges. My new shop redid the hinge design to make it fit properly and move flawlessly and without effort.
one more thing - if it's not a show car both are very stupid to do on a daily driver. both are a total inconvience to the driver and the passengers for everday use and I would imagine that neither should take daily abuse. I've installed expensive and cheap KITS on on Civics and RSX's and some other cars - these kids put them on their daily drivers and often have to come back for adjustments and i'm sure eventully replacements (shocks) since they are not made for daily use. My SVT is a full show car and a once in a while sunny day weekend car thus I spared no expense and my door hinges are welded to the car for safety reasons therefore making them permenent.