Visiting St Petersbourg (St. Petersburg)

Hello everybody,

I'm a Parisian guy living and working in Munich and I will be 10 days in Russia for Easter at the end of April.
If one of you could give me some advices, it would be great : what should I see in the city, how many days you advice me to stay, do you know some good places to stay ( youth hostel could fit ), where should I go out etc..

Thanks a lot !

Fabrice