Hi, Just a screen call from one of the biggest IT company in the World, and after 30 min, they told me that they offer me face to face interview-tomorrow!. I am really happy about it but nervous too

. If I would be successful I will need to relocate. Do you think is OK to ask if a company offer relocation package and when I should ask?. I need to admit that I am still studying and at the moment I am not expert with Windows and do not know almost anything about Linux-which they required! . Just a medium-level knowledge of Windows. They required Windows/Unix knowledge. What I should answer if they ask me about Linux? Shall I say that I do not know but I am willing to learn?. I want admit that I didn't lie about knowing Linux, that's way I am surprised that they offer me a an interview!
Any advice?