Hi,
From Sousse to Tunis it's something like an hour and half driving ... i think it's 140 Km, i donno what's that in mile ...
To go from Sousse to Tunis and vice versa is easy, you can choose between the train, the bus, and the Louage ( a car painted in White and Red) if i'm you i would choose for the last one ... about the prizes it doesn't cost anything ... it's something like 8 Dinars ... ( 5 Euro's , 4 Pounds) ...
To have an accommodation in sousse is easy and simple ... but it depends on your budget
if you have money for sure you won't have any problem finding 5 stars hotels
... but whatever ... i believe you will be able to find accommodation always in Sousse
Cheers
Makrem