Construction contract?

from the time i entered a contract to perfrom work for a school, i hae since changed my business name and federal id # (changed from corp to LLC). i want to know how to go about notifying the school about the change and get paid under the new name when i start the work. (havnt started yet). do i write a letter, do it in person, is it a amendment, addendum, or modification to the original contract? i hope this get to some people who know and can help. any info is great.