Not an expert. But that would cost the Germans a lot of troops and equipment. All that they need desperately for other, more important campaigns.
Undoubtedly they would do it seperately, as they can't afford to move more armies around whilst France still needs to be beaten, they were heavily preparing for Case Yellow. So it would probably happen instead or alongside the invasion of Yugoslavia, early 1941?
The chance of winning is good though, i don't think Sweden was prepared to face an invasion. However, troop deployment by Germany in Norway(which they need to do as a naval invasion is suicide) would prompt the Swedes to start preparing defenses and their army and defenses were more formidable than the Norwegians. And like all other nations facing the nazis, they will defend fiercly. Their ability to defend concerning terrain is very positive and the Germans will have a hell of a time breaking it, costing them a lot of men and material. All that they need for Barbarossa.
Don't know the position of Finland in this suitation though. They might join in?