Maya - Light map question

frizzledcat

So I am making a crate for a group project that is going into Unreal.  I am still a little new with some of the prop workflow.  But anyways I made a crate in Maya, unwrapped it and then textured in Substance Painted.  But someone said I should set up Light maps.  
So I followed a light map tutorial, following along with a separate file.  But at the end I realized a question.  Can I use the prop I already textured and add a light map to that object file or should I start with the version before i brought into substance painter.  
Sorry if this is a dumb question.  Thanks very much.  

Fingus

A light map is just a second set of UV's that won't have any effect on your primary UV's or textures, so you should be safe to just add that to your finished asset.