There is a search window at the bottom of the discussions index. There are literally hundreds of threads about this topic...but since you are new I'll repeat my advise about careers in arch right now - don't waste your time. The market is in the crapper for probably a prolonged period of time that could bypass your architecture education. Pay is poor and often not practical for anyone who has been "out there" for a while already. Pursue a more viable career.

You would need to look at an MArch I first professional degree. A BArch would take up unnecessary extra time since you already have an undergraduate degree. You can get into MArch I programs without having had an undergraduate major in architecture, although they expect their applicants to have taken a few relevant undergraduate classes such as art or architecture history, physics and calculus, and art or architecture studios. (The requirements vary depending on the individual school.) Indeed, the architecture graduate schools especially like applicants with have non-architecture backgrounds, since they bring a diverse variety of perspectives to the school.

For your portfolio, the grad. school admissions committees are not so much looking for mastery of the technical side of architecture, but rather evidence of creative ability and potential. You can and should include a lot of your art work. Generally the admissions committees like to see documentation of the creative process behind a work as well, such as initial drafts and sketches. That rule applies more directly to architectural design projects, but might still be worth keeping in mind. For examples of other portfolios you can search through the forum, especially the "commiserate here" threads.

MArch programs close to New York City for you to look at could include Yale, Princeton, Columbia, and Pratt. After you graduate from a professional degree program you'll have to go though a grueling internship period called the IDP before you can get an architect's license. It's supposed to generally take 3 years, but can take longer in practice. More information is available here: http://www.ncarb.org/idp/

Architecture is something that you should make sure you really want to do, so you are on the right track by wanting to learn more about the profession before you commit. The Harvard GSD has a career discovery summer program that comes to mind, and there are several other similar programs out there. An internship might be kind of hard to obtain if you don't know AutoCAD and/or Revit. A construction internship might also give you more perspective.

There are a lot of people who think that they want to be architects and then lose interest once they find out what the profession is really like, but IF you do find that it is something that you want to do then don't let the current (and ultimately temporary) economic situation affect what you want to do with your entire life.

yeah, don't get a b.arch when you can go straight for an m.arch.

don't fret about being on the trading floor now, at least you'll have the money to properly fund your education.

if youre sure you wanna go into architecture, just put your stuff from your sculpture studies in a portfolio and go apply. if you're not sure: go work for a firm for a while and/or do one of the summer programs at columbia, harvard, etc (i think ucla has a good one too). preferrably both because practice is generally quite different from school.