Spark plugs are one of the easiest things to change yourself, especially on 4-cylinder engines. All you need are a few basic hand tools.
A set of 4 OEM spark plugs costs 40-50 bucks. Labor should be under 30 minutes even if you are new to working on cars. $300 is a robbery.
Here's the Amazon link for the spark plugs:
http://www.amazon.com/NGK-93618-SIKR9A7-Laser-Iridium/dp/B00P179D2S
Also, for what it's worth, I'm pretty sure you can get more than 30,000 miles out of your OEM spark plugs.
The OEM plug for the Dart Turbo is a NGK Laser Iridium plug, which is similar to the plug used in just about every single modern Honda/Acura. In those applications, it is rated for 100,000 mile service intervals (including on the turbocharged Acura RDX). Then again, Dodge is not known for reliability, so it can't hurt to change it at 30,000.