Don't be a jerk, but do challenge him on what he says. He will tell you what he knows and you will find out what he doesn't know at the same time. I would not dismiss him out of hand or feel cheated though, because MOST instrument ground instructors are newbies. He is probably at least competent, and IFR ground instruction is mostly facts and rules, hard to mess that stuff up. Flight training towards an instrument rating is another beast. An experienced IFR flight instructor is worth his or her weight in safe flight hours and a lot of them are time builders. My IFR training was fairly weak, and it came to haunt me later on. I got my CFII from a very advanced fellow, and only then I realized how weak the first round had been. It was a minor marvel I passed my initial instrument checkride without a retake, given how weak my instruction was.