Tiva C series TM4C123G launchpad is a result of renaming Stellaris microcontroller line in to Tiva. Both launchpads carry practically identical microcontrollers just with different tag. This probably caused some confusion when setting tools and using libraries. Practically speasking if have a working binary compiled for Steallaris launchapd, it should work fine with Tiva launchpad. Anyway if you just warming up with Texsas Instruments ARM Cortex-M4 microcontrollers, you will definitely have to start with Tiva C. It seems that TI is trying to make Stellaris name thing of past despite current Stellaris Launchpad popularity and availability.
Tiva Launchpad have pretty good support and educational materials at their site. But it is based on CCS tools that are limited for free usage. Full functionality is limited time and then code size is limited to 16kB what is not enough for ARM micros. As any ARM cortex microcontroller Tiva can be programmed with GCC tools. It may be quite tricky to set things at the beginning, but once set you can focus on work and have same results like with paid tools. In this small tutorial Scienceprog walks through how to set up a project template for Tiva C launchpad using Eclipse and Courcery Codebench Lite tools. This is mostly derived from Stellaris Launchpad template found at Kernel Hacks. When comparing to Stellaris, Tiva libraries and drivers differ a bit due to changes in TivaWare. So probably using new template can be a time saver while setting a new project.