Drop juice in iPhone 4s screen

Hello,

I dropped some pulp juice at screen of my IPhone 4s.. Now don't work!...

I cleaned then use vacum cleaner and hairdryer ...

But the screen stills black, don't give any sign.. it's a damage motherboard?

Is possible to change it?

Also 2 weeks before, had other problems.... starts with some breaks, also when somebody call, don't give me any sign or sound, the screen is black again but with some sentences about "can call later" and so on...

I really dunno know what to do.. since I use a plastic cover with doble screen, it wasn't so wet..

I bought the Iphone in USA, but I'm from Europe (no garanty).. is from this year pretty new, never fall down and only 2months ago I start to put some app...

I need some advices!?? Please help! :,(