Auto refinance with bankruptcy background

[YERH]

I purchased a 2004 vehicle in March 2005 at a rate of 18.97%, the higher rate was on account of a filing for bakrupcty on Nov 2003. I set up for the payments to be (ACH) automatically deducted from my account by the lender so that I would always pay on time. I recently received a letter in the mail from HSBC bank stating that because of my good payment history blah blah I was qualified to refinance my car loan for at least 5% below the current rate. I called, was approved and this is what they said:

current loan
pay off amount is $9,224 @18.97% with payments of $303.16 p.month and 42 months remaining of payments

refinancing option
$315.00 due per month @ 13.97% for 36 months, or
$251.94 due per month for 48 months.

My question is :
Does it make sense for me to refinance at the above rate and savings of $1,315 (no payment due for a month) or would it be a better option to send the current loan company an extra amount with each payment that would apply to the principal and hence lower the life of the loan anyways?

What are the repercussions of having a refinancing on my credit history and what would happen if I turn down this refinancing approval after I acccepted it over the phone? (waiting for contract on email to sign and close).

Thank you