3.5 years = out of warranty = ouch!
The good news is that its just the battery, not the laptop itself.
The bad news is that Macbook batteries are not 'user replaceable', any Apple stores nearby?
Most Apple stores can replace a Macbook battery in short order, since they hav the tools necessary.
They usually recommend you call ahead to make sure they have a replacement battery in stock.
You can always call Applecare and arrange for service. They will send you a padded shipping container
and shipping instructions, etc.
Aaaaaah, I probably don't need to tell you this, but if you send your laptop for service plug that puppy
in first and 'scrub' the hard disk of anything you don't want the world to see. One can't be too careful, can one?
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