smoke. blinking check engine. runs rough. sudden onset.

[Mous]

Greeting fellow enthusiasts, and you other guys too. '97 outback, Coming back from the store, going uphill the engine started smoking from under the hood and sputtering, The check engine light started blinking so I stopped to let it cool down & compose itself. drove home ok (about 3 miles level ground) light stayed on but not blinking. Last week the engine light came on too. Those OBD2 codes said misfire on 2 and 4, so I replaced the front plugs and the hot wires, cleared the codes and no problem till today, now the code says misfire on #3. I'm guessing a sensor is malfunctioning somewhere. Can someone here suggest anything? Passenger side headlight also went out though that might be coincidental. Thanks and obsequities

PS what's the trick for removing the back sparkplugs?