im in the phila area and have used my former block heater 2-3 times in 30yrs, and once or so in 10yrs up around ny. glow plugs working is universal to cold starts in all weather.
745 The reason you are getting shocked is likely due to a pinched or frayed wire crossing over to the metal ground of the car. You touch the car and connect it to ground zappa roo. Hey that hurts!
The block heater cord SHOULD be grounded which would make that impossible too. Sounds like a bad cord and/or heater.