I have enrolled in a course from october to march (under 180 days) at Universidad Complutense. I will be going to Spain end of September on a student visa and I am a US citizen. I am applying for the Escuela Oficial de Idiomas also. The EOI course is 1 year long and I can stay longer than that if I want.

My questions:
1) If I can get into EIO can I renew my student card and stay here as long as I am in school studying?
2) Can I renew my student card in Spain?
3) Do I need to renew my student visa?
4) If yes, can I renew that in Spain?
5) Can I get an NIE and a Student card

anton,
the language courses in eoi are year-long courses, so if you are enrolled + meeting the other requirements of the student card, the card is renewed for another year. spanish is intensive, so one level a semester or two levels a year. at present there are 6 levels. the levels of the other languages offered are yearlong.
you need 15-20 hours a week of study.
if you enrol in spanish only, that is enough.
if you are taking yearlong courses you have to take 3 languages to cover the load requirement of the student card renewal.
student cards are renewed in spain before expiry date.
upon entry with student visa, you have to apply for the student card before it expires.
as soon as you get a room or housing and get “empadronado”, submit all requirements for the card.
the card comes with the nie number.

Spanish is or isn’t enough by itself?

anton,
if you are enrolled in spanish at the eoii, the police will consider that enough load.
ah, you have to get true copies of your high school transcript and diploma.
get them apostilled. google apostille and your state to know the procedures and have them translated into spanish at the spanish consulate.
you need this document to be able to apply at the eoii.