Forgive my brevity, writing this on mobile in the northwest of Poland right now, so I'll try to reply better when I'm not so limited. I also suspect most of the Poland experts here are on holiday right now.... Or at least one is.

In terms of Krakow, getting in and around is best done without a car unless you intend to see sights outside the city. In which case a hotel with decent parking is essential. But in and around the old city and Kazmierz you definitely want to mix the ubiquitous tram network with walking. The 50 that runs down Starowislna takes you from just outside Kazmierz to the main railway station.

Things I'd recommend seeing include the museum under the main square, Kazmierz in general, Wawel (go early, it gets sold out), but others will have suggestions as well. I'll try to remember to get back next week when I'm back and put together some more suggestions...