Hi there,
Change is simple and easy ... in the centrum of each city there are plenty of banks ... there can you change ...
in the hotel as well ...
in the street but it's illegal .. you can make more money by changing in the street ... but it's not legal ..
credit card you can use everywhere as well .. but what i do myself .. and i believe it's the best way ... i take all the time my normal bankcard .. and i just use it to get money from the machines in the street ... (machines are everywhere ) why i believe it's the best way : First then you are using your own money (it's not a credit ) no interest over the money you use in Tunisia ... Second : if in case you use it .. you just contact your bank and it's blocked ... Third : in case you have a problem with money ( money ba777 / i mean OVER

) you still can deal with your bank ...
Take it easy and spend as much as you can in Tunisia ...
Rgds
Makrem