Update...
I brought my vehicle back to Firestone of S.F. today and was treated fairly and with respect. They resolved the issue of oil pressure switch and the miscommunication quickly and professionally. They appologized for any inconveniences that may have occured.
I also aplologized for my hasty review of their service. I have been a Firestone customer for years and have had little reason to fault their service or professionalism in the past. It matters little now if there was a simple miscommunication or an incorrect price quote of the unit. What matters most is that I recognize that I am human as are the service reps and mechanics of Firestone. We all make mistakes. Firestone of San Francisco's past performance should have made me recognize that I do trust them with my automotive care and they will continue to get my business in the future.
I was too quick to judge a company that has served me well in the past. Let this update help others reading these reports to recognize that simple miscommunications or other issues should not be reason alone to cast misjudgment. Give them the chance they deserve.