I doubt that there is a direct bus, besides there are almost no freeways in that direction. For trains most of the way is on so called corridor where trains can go up to 160 km/h. I would take train. There is one direct train which is overnight. Starts in Wien Westbahnhof, leaves Wien Hauptbahnhof at 22:39, arrives in Oswiecim 5:05. It goes all the way to Krakow but you get off in Oswiecim. Then there is one train where you have to change once. The train leaves Wien Hauptbahnhof at 8:07, arrives to Katowice at 12:37 where you get off, the train then continues all the way to Gdynia. Your train to Oswiecim leaves Katowice at 14:40, arrives in Oswiecim at 15:42. (It is direction to Czechowice-Dziedzice). All other connections are with two or more changes.