all the many deutsch dialects

i keep hearing many different things regarding this issue, so someone please enlighten me :]

is it true that if i were to go to the northern cities of Germany, i would be hearing a form of the German language that was very different from that spoken in the southern cities of Germany? and does the same apply to the east/west cities, as well as the German spoken in Austria? I have heard that for sure, the German in Switzerland is markedly distinct, but I had really thought that in Germany at least, the language was fairly homogenous. is the standard, or 'high' German, considered the most proper or formal, whereas another type is considered the colloquial spoken form?

i'm considering going to Munich or Frankfurt in September with my mom, maybe there is a better city we should look into visiting if we want a really good exposure to the language? (at least, that's what i'm into, i think she's more into the shopping!)

thanks guys :)