Process is like this
1)Purchase car in washington, get bill of sale and title.
2)Fax the bill of sale, title and import form (can be picked up at US customs) 72 hours before you plan to cross the cdn border with the car.
3)Upon arrival of the border (Truck crossing) First go to US customs to export the car. Assuming you have filled out the necessary paperwork correctly US customs will verify that the registration number on the car matches the information on the title. Once this is completed they will stamp your title and you move on to CDN customs.
4)CDN customs just want money. You will be expected to pay the gst for the purchase amount listed on the bill of sale as well as 6.1% duty.
5) The vehicle must then pass a "BC Vehicle inspection" test, which everyone makes out to be an incredibly large deal but they just test to make sure all the necessary things are working and that your car isn't a rust bucket. Ie. transmission, brakes, no rusty heater channels/floor pans, windows roll up and down, windshield wipers, seat belts etc. The cost of the vehicle inspection varies from location to location, ours was 80.00 which was 65.00 for labour, and 15.00 that goes to the gov't. Once your car has passed the safety inspection you go onto ICBC.
6) Bring your passed inspection form, pay your pst and insure your car.
Is it a big deal? No and you come out with a car that's much less rusty than anything you would find up here and don't have to waste your time with body work etc.
Good luck.