I have TivaWare SW-EK-TM4C123GXL-22.214.171.124 unpacked on my system.
I know there are more recent versions.
It includes a 'doc' directory with many PDFs, like SW-TM4C-EXAMPLES-UG-126.96.36.199
which is the TivaWare Examples User Guide.
The examples themselves are under "examples/peripherals/"
There are many sample projects under the "examples/boards/ek-tm4c123gxl" directory, too.
It takes awhile to get used to where everything is and how it works, but it's not difficult.
Sometimes doing things in the analog domain can be a viable option. Your requirements said "peak detector" to me when I read them. See the links below for some info on peak detectors and you may be able to find integrated solutions from the likes of TI, Analog Devices, Maxim, LTC, etc.