I had my 2013 Model S in for the eMMC recall/replacement. While I was waiting on the eMMC part to arrive, I messaged the TSC asking what the cost would be to replace my 3G modem with the 4G/LTE board. TSC in Decatur, GA quoted me the parts-only cost for the replacement ($118.21). Plus they fixed a missing clip that was behind the dash. The service advisor even said, great idea replacing the board while we were replacing the eMMC card, saved yourself $400.
Hope this helps others upgrade to LTE while getting their eMMCs replaced.
Hope this helps others upgrade to LTE while getting their eMMCs replaced.