Regarding your questions
1) Incorrect information on style of the vehicle and expiration are not likely sufficient to persuade a judge to dismiss your ticket.
2) BC has a reciprocity agreement with Washington RCW 46.63.020. http://apps.leg.wa.gov/RCW/default.aspx?cite=46.23.020. Therefore, it is my understanding that ICBC may receive notification if you plead guilty
3) Attorneys generally fight tickets for a flat rate of $175 to $350, but sometimes you get what you pay for if you just focus on the cost. Experienced traffic ticket attorneys rely on technicalities to get tickets dismissed and generally stand a much better chance in getting tickets dismissed or reduced to something that doesn't impact your driving record.
You may also want to consider a deferred finding if you are eligible as one possibility to keep the ticket off of your record if the court allows you to do this by mail. (You can call the court clerk and ask). Deferred findings are explained on this page. http://seattletrafficandspeedingtickets.com/ticket_practice_areas/faq.html Please note that experienced WA traffic attorneys will try to get the ticket dismissed outright or reduced before resorting to a deferred finding which carries some risk.