Repair shop broke off spark plug in my Montero

My vehicle is a 1987 Mitsubishi Montero (under the Dodge Raider name) - the original Raider which was a 2-door Montero. It has 210,000 miles on it and has a 2.6, 4 cylinder engine.

I recently took my vehicle into a shop (one that I never used before but came highly recommended to me) to find out why my car was running so rough. The mechanics decided to start by looking at my spark plugs and one of the guys managed to break off the plug. Another mechanic told me that he could not get it out and told me that he would spray a lubricant on it and informed me that I would have to leave the car overnight.I guess to see if the lubricant would help loosen the remainder of the plug. I was told the next day that they still could not get the plug out and so they used some sort of extractor tool and managed to break off that tool also and left a piece of it in my engine. I did find someone to help me get the piece of the extractor out but the coils of my old plug are still stuck in the engine. A couple of people told me that it might be possible to get that piece out if they used a torch to heat up the engine. I don't know if I want them to do that however for a few reasons but am wondering if it would be possible to use an industrial heat gun to loosen that part. At this point, all I want is to get the car running again without spending a lot of money on repairs. Would using a heat gun work on this situation? Any other suggestions?