I'm a Greencard holder here in the US and I'm planning to study in the Phils. Can I stay there for 3-4yrs?

I dont want to have problems with my immigrant status. But I would like to study Nursing in the Phils w/c means I need to be out of the US for 3-4yrs. Is is possible to request for (like) a study permit? What if I bring my US born son with me, will there be any problems if he'll be out of US for the same period? For those with knowledge on this issue and/or had similar experiences, please help!!!

You need to apply reentry permit (i-131) BEFORE leaving. It serves as an entry document when you return and it's usually valid for 2 years from the date of issuance. the reentry permits cannot be renewed and can be applied for only inside US. If you If you are absent from US for more than 2 years, you must return to US to apply for another reentry permit.
You can do it without an attorney. here is the link to form i-131.
http://www.uscis.gov/portal/site/uscis/m...

http://www.uscis.gov/portal/site/uscis

Unless your son has a US passport, there is no way for officials to know his status (since "9/11" birth certificates are no longer accepted at borders).

I'm puzzled by your desired to study Nursing in the Phillipines (at least, I presume that's what "Phils" refers to, as opposed to an easily understood typo for "Phila" meaning "Philadelphia"!). You didn't say where you live, but I can't imagine why you wouldn't want to be trained in, arguably, the world's finest nurse-training facilities, right here in the USA? Even if the cost is cheaper to train in the Phillipines, how are you going to live? What about transportation? Some US medical offices and hospitals might require you to take additional courses on top of whatever degree or certification you get overseas, so, again, what would be the point of studying, there?

Regardless of your reasons, the first link has an excellent article, which covers your question, almost perfectly! The second link tells what you need to provide proof of your child's citizenship.