So take it back, and if the idiots at the Apple store won't do it, look for an AASP in your area. They have the same training and tools (sometimes even better ones) than Apple's "geniuses".
Frankly I've never been overly impressed with Apple's in-store service. They always seem to be in a rush to get you out, since you're not buying anything. Plus, Apple store techs get to be lazy. Since Apple isn't paying out labor reimbursements, they get to just toss part after part at a system until they stumble across the solution. The problem with that, is every time you remove a part from the system, you introduce the chance for ESD damage, not to mention other possibilities.
An AASP has to worry about what Apple calls a Service Excellence score, which determines the rate at which they pay labor reimbursements. AASPs are expected to fix something with only one part, the repair turnaround time is supposed to be 10 days or less, and if the system comes back within 30 days, that dings the score too. So AASPs have to actually know their stuff, they can't just throw a dart at a picture of a system to decide what part they're going to replace until they find the one that fixes the problem. Your AppleCare agreement is valid at any AASP, so Apple will pick up the tab for your repair, and you'll be helping a small business at the same time.
If the Apple store doesn't want your business, take it somewhere that will actually value you as a customer, and will take the time to make sure your system is good as new.