1998 Mazda Millenia • 157,000 miles

I have a 98 mazda millennia. I took it to the shop for a plug/wire replacement and they told me that the valve cover gaskets were leaking oil into the spark plug housing and that they would likely need replaced again every 5 months or so. How much should valve cover gasket replacement cost? I can't remember what they estimated.
Additionally, I am in dire need of an alignment-I really should not even be driving it at this point. It is extremely squirrely at high speeds-dangerously so. When I visited the shop to have one done, the mechanic told me that they could not do an alignment without also replacing the cv boots. For the cv boots they gave me an estimate of about $600, and a shop down the street said $500. Is it really necessary to do the cv's before doing an alignment? And also, should it really be that expensive? It seems like an upsell to me, but I don't know enough about cars to dispute it.
Also, I live in minneapolis-I know the cost of living is higher here than in many cities, but a lot of people are telling me that cv boots shouldn't be anywhere near that expensive.
Thanks for your help.
December 1, 2012.

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