Prices vary widely by region (the 30K service is
$479 in Silicon Valley where labor is very expensive).

A local mechanic can do it. As long as you keep records then
there should not be any future warranty issues.

Advantage of a dealer is you can get warranty work at the same
time, they keep records for you, the techs know common problem
areas well and often pro-actively check these things out, loaner
cars provided, and they run a recall check and will apply any
recalls as needed. (Above from a good dealer, of course.) A
good independent can probably provide all of those services
except the warranty work, too.