1997 altima problems

Hi. I've got a 1997 Altima that has suddenly become a problem. About three weeks ago, the service engine light came on, so I took it to the garage to have it checked. They said the code was for the mass air flow sensor. They also said there was a problem with the exhaust system. The charge for replacing the maf sensor was $600 and they wanted another $500 to fix the exhaust. I asked if having the maf sensor replaced and waiting a month or so on the exhaust system would hurt anything. They said no, so I had the maf sensor replaced but nothing was done about the exhaust. Now, three weeks later the service engine light is back on and they are saying I need a new egr valve and egr sensor. Are all of these things related? How much should I expect the egr valve and sensor replacements and work to cost? Would fixing the exhaust solve all these problems? I hope someone can help me out. I'm waiting until Monday to tell them what to do. Thanks in advance.

Sounds to me like you should have yourself a second opinion. Unless you just have about the worst luck possible, all of those parts should not be faulty at the same time. What did they say is wrong with your exhaust anyway? Whatever the case, the exhaust should not affect the MAF or EGR. The MAF and EGR both deal with the intake of air into your engine, so they could theoretically be related, but I highly doubt it. If I were in your shoes, I would be extremely reluctant to believe the mechanics at the place that you are bringing your car because it sounds like they are just a parts replacer as opposed to an actual mechanic.