Get it fixed?

My sister-in-law had a broken dryer. I looked at it and said, "Yep, it's broken." Fast forward a few months and they got a new one from Habitat. Of course the plug they have is a 4 prong and the cord that came with the new dryer is a 3 prong. SIL goes to Ace, and the jackass working there tells her, "Oh you don't want to switch the plug on the dryer, that's a real pain. It's MUCH easier to switch the plug on the house," and sells her a new 220 3-prong receptacle. I come over and see they have a new dryer, look behind to see if it is hooked up and see the 220 with the cover off laying on the floor. I ask her what the hell she's doing and she tells me that's what the guy told her to do. Fortunately she knew enough to turn the main breaker off while messing with it and at some point decided she was over her head. Thank God I caught it in time. I wish she would have just asked me though because I switch plugs from the old to new and had them up and running in about 10 minutes tonight. I want to go punch that guy at Ace in the junk.

Am I wrong on this?