Hi, I worked in the US with a J1 Visa for four months in 2007/2008.
I just received my W-2 form but I'm not so sure what to do with it. I want to do it myself, but people keep telling me different things about what forms I need to fill out.

Can somebody tell me what forms I have to fill and how do I get them?

On J1 you are exempt from residency for 2-years. You must file non-resident tax return Form 1040NR or 1040NR-EZ and Form 8843.

Your income is not subject to FICA taxes but you must pay federal and state income taxes.
Read: Your U.S. Tax Return: U.S. Tax Filing Requirements for Non-Residents

Y estos formularios los puedo bajar de internet nada mas?

Can I download those forms from the internet?

Yes, from Internal Revenue Service

Thanks!! :)