It could be many things, one of which is worn out brakes. Even if it is
brake squeal, it's also possible that it's normal, too.
As far as your warranty goes:
1. Your brake pads are no longer covered. Warranty on pads is 1 year/12k
2. Your bumper-to-bumper warranty is almost over (60k). If you think you
may have some sort of warrantable issue, you should probably get to the
dealer right away. The down side is that if it's not warrantable (such as
brake pads), they're likely to charge you a diagnostic fee if you don't
have the work done there.
3. The brake pads have just about nothing to do with any powertrain
component. So if you're the original owner, that should still be good
until 10 years/100k miles.
You're likely to find that the chain shops are not willing to do the
$39.95 lifetime-warranty special unless you repair other things the find
defective (maybe "defective," if you get my drift). I'd think your best
bet on brake repairs would be a well recommended local shop who can be
trusted with advising you honestly. You're likely to avoid the chain
come-ons that you've mentioned as well as the higher costs associated with
many dealers. Don't be afraid to shop around. One dealer where I worked
priced brake work specially to remain competitive with nondealer shops.