Austrian-German vs. German-German
I am looking to do a study abroad program and I found one that would work well for me in Vienna. Originally I had been planning to go to Germany. My question is, how different is German-German from Austrian-German? I've grown-up learning German that I think is a northern (Hamburg) accent. I don't really want to have an Austrian accent as my family is from Hamburg. I am planning to go abroad for about three months. Do you think I would acquire a new accent if I went to Vienna? My other problem is I have many years of study in German-German and I don't want to suddenly not be able to understand things in Vienna that I would understand with ease in Germany. I am still looking around for programs in Germany, but I do want to visit Vienna. How much of a barrier do you think it would be? How different are the accents? What about the vocabulary? Can anyone give me some examples of some differences (I've already heard of Gruess Gott)? Any thoughts or insights are appreciated! Thank you!

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Answer

In Vienna (as well as anywhere else in Austria) you will hear anything between clean Standard German (with a couple of special Austrian words), Standard German with a recognizable Austrian accent and the actual local dialect. The first should be easy to understand, the second requires maybe a couple of days to adapt your ears, and the last can be quite challenging for any foreigner. Yes, you will probably acquire a slight Austrian accent, but if you stay in contact with people from northern Germany, it won't be too strong.

Wikipedia has quite a long list of special Austrian vocabulary. Some of the words on this list are very specific to special situations, so that you will hardly hear them, but others are very common in daily usage. Some of These words are also used in southeastern Germany, but most of them are clearly Austrian.
https://de.wikipedia.org/wiki/Liste_von_Austriazismen

Answer

Will you acquire an accent? Possibly, but you would lose it again as fast as you'd acquired it.
The thing is: there is no dialect-free region in Germany, i.e. wherever you go, you'll be confronted by the local dialect to some extent. However, educated people usually speak with only a very slight regional accent (or none). Therefore, you will be able to understand people at the university of Vienna just fine.
There are a few - but not very many! - words used in Austria which people in Hamburg would not understand, e.g. "Obers" instead of "Sahne" for "cream". But "Grüß Gott" is used as a greeting all over the south of Germany as well. 
If I were you, I wouldn't worry too much about this. :)