What would you suggest for a raised bed I have made of old railroad ties that id like to turn into a vegetable garden? Should I line the bed with something and replace all the dirt first?

If these are old creosote soaked railroad ties I would definitely line the bed to keep that stuff from leaching into my vegetable soil. It's been years since I was around that stuff but I recall it as stinky tarlike & would be leery of eating anything that grew out of it.