As a first step you need to have a meeting with the credit union to see what your options are. They are normally great to talk to so it's time to sort it.
You say the guarantor is struggling financially, but would he be able to repay the 14K? Ultimately if you cannot pay he is liable, if you're close to defaulting I think you need to tell your friend what is happening so he can prepare for the worst. Do you have any assets?
You haven't given us much information about the loan, nor your income and outgoings etc.