MS systems enough?

I’m a new immigration in Toronto. Just came here several months ago. Have been working as a Network/Database administrator for about 5 years. What I did b4 mainly focused on MS operation system like MS NT/2000/SQL, and I’m a MCSE (2000)/MCDBA. So should I keep focusing on it? Or spend some more time on other OS like Unix/Linux? But without a production environment, what I can learn might be limited and couldn?t get into it thoroughly. Really feel confused now, if anyone can give some advice on it will be highly appreciated.
BTW, could somebody tell where I can find the good information/websites online about Linux/Unix/Oracle.Thanks again.