Hi!
You can specify tracking number for orders on any order page:
http://awesomescreenshot.com/0c63581n8d
Besides that, I believe, all webgility modules should work properly on 5.1. They updated the modules several weeks ago. If you feel, there is a problem with modules, please contact them at
sales@webgility.com as specified here:
http://www.x-cart.com/extensions/addons/shiplark-by-webgility.html