Is BofA going to charge you a fee to do this conversion?
That is an important point you are making. It is definitely important to find out if there are any loan processing fee to process the loan. Also it is important to find out if there are any prepayment penalties for paying off loan early. Often both the loan processing fee and prepayment penalties will be minuscule compared to the amount of interest saved. Agreed that you should still do your homework to be sure of how much you are actually saving. The single biggest factor after considering everything is how much lower is the new interest rate compared to the old interest rate
If the old loan interest was 5.5% and the new loan was 4.5%, that 1% difference interest rate might not be much of a saving after considering fees. On the other hand if the interest rate is significantly lower, the savings may be substantial regardless of the fees.