The Janet 737s have been visiting Goodrich Aviation at KPAE. Comparing
page counts from the FAA I already purchased, it looks like on N5294M
is the only 737 that has had it documentation updated. [It is possible
the page count record provided by the FAA is wrong.]

Photos of Janet 737s at KPAE:
http://microvoltradio.com/janet.htm

Two pages indicating the repairs. Nothing exciting here, but that's
how research goes:
http://www.lazygranch.com/images/janet/n5294m_goodrich_1.gif
http://www.lazygranch.com/images/janet/n5294m_goodrich_2.gif

N654BA had an antenna mounted on one of it's windows. From the
paperwork, the function of this antenna isn't clear.