Heyho,
If I remember right you must take fully datafolder, load Tcds and start do this:
About maps, there are changes in Map loading in TEngine. Loading old datafolder is similar as loading new datafolder. There are some values which aren't exist in older mapfiles. So you must delete them. I'll not say you what you need delete. How about find it on your own.

Next step is load Img folder, that means rework interface. That contains old login functions or char select etc.
A little help: Login screen is some ObjID.