Your  packet can be mailed to any one of the 17 Regional Exam centers listed on the website.
  http://www.uscg.mil/nmc/checklists/master_100.pdf

Information about Merchant Mariner License without enough sea time from the Coast Guard, you can renew if you follow the proper procedure below.

Good Morning,

I received your letter and this is what you have to do to renew your license. You will need to file out an application I will need a physical, drug test and a copy of your TWIC card. Since you do not have 360 days of sea time there is a take home exam that you can do it is an additional $45.00. Once you apply to renew your license the National Maritime Center will send you a letter saying that you have been approved to test and then we will send you out your examines. The renewal fee is $95.00 and the take home exams are $45.00 total $140.00. You do not need to go to the REC in New York you don't actually have to go to an REC you can do it all by mail now. Just send in your application physical drug test the copy of your TWIC card and a check or money order for $140.00 and state on your application that you want to do the take home exam that you don't have enough sea time to renew. If you have any other questions please feel free to contact me or you can contact the National Maritime Center at 888-427-5662. Thank you and have a great day.

U.S. Coast Guard
National Maritime Center
100 Forbes Dr. Martinsburg, WV 25404
(P) 888-427-5662
(F) 304-433-3416

The fee can be paid on www.pay.gov. The fee for renewal is $95 not including testing, the testing fee for a renewal is $45 if needed, the fee for a new license is $140 not including any other testing fee's.  this is the info from the USCG Center