IBM 5140 - Some Documentation Pointers
"An Introduction to the PC Convertible"
Pages 1110-1115 (PDF pages 1142-1147) of Upgrading and Repairing PCs - Tenth Anniversary Edition
IBM manual - 'Technical Reference'
There is a link to the technical reference here.
Additional information
There is a lot of good technical information on the IBM 5140 page at ohlandl.ipv7.net; a link to that page is here.
Optional CRT monitors, and CRT display adapter
See here.
AC adapter
See the VCF threads at here and here.
Battery pack rebuild
See the VCF thread at here.
A discussion about paper for the printer
See the VCF thread at here.