i know i can do the job with my eyes shut,
And remember that, it's not the job making you nervous as you know the job and enjoy it, it's the people, so you make sure that the people like you and want to work with you, make sure that you smile and appear friendly and confident, you can be confident because you know your job and remember your to be an asset to them, Roxylola says it all in that if you don't know, or your mind goes blank just be honest, there aren't many of us who actually like interviews and don't get a little nervous, people expect that. :-)
Do you have a portfolio of dogs you have groomed too, it will go a long way, along with qualifications and references?
I've always had the mindset of get in there do the interview if your meant for the job you'll get it, if not never mind something else is waiting for you, no point being nervous about it, what will be will be..... believe in yourself and others will too. :-)
I wouldn't be worried, I'm a groomer too part time and even after nearly two years of working in a salon I still ask my boss occasionally which blade she thinks would be best with particular coats as let's face it sometimes we all miss the obvious! Better safe than sorry, and they'll appreciate that.
I would bring a portfolio too as you want to show your technique and finish and styles, some groomers do things differently after all.
Oh, and good luck!!!