Can I marry if my visa is still valid and will I have a chance at becoming legal, staying, and being able to work?

Although not entirely clear from your question, I presume that you are asking about becoming married to a U.S. citizen. Generally, someone who entered the U.S. lawfully and with inspection (such as with a visa evidenced by an I-94 Card), may marry a U.S. citizen, and then promptly apply for adjustment of status to become a Lawful Permanent Resident (to get a "Green Card"). This is true regardless of whether the foreign national spouse may have overstayed his/her visa or even worked without authorization. It would be wise for you and your fiance/fiance to consult with an immigration attorney who, after learning all of the relevant information about you and your soon-to-be spouse, could advise about immigration eligibilities, options and strategies and offer legal representation in the often complex application process. Some immigration law firms, including mine, offer legal services on a "flat fee" basis so that a client will know the total expense from the very beginning, and a few immigration law firms, including mine, offer an initial consultation free of charge.