I am Canadian and I have bought and sold a ton of parts across the border using only Canadian postal money orders in US funds which we have to pay for in full at the going exchange rate at our Government run postal service so if your Banks have an issue it's because they haven't got the info on them they are as good as cash and all banks will not release the funds until it clears, so just wait until you have the money clear and send the parts you have no worries and as far as being held accountable for the funds up to a year i doubt it as there is no reversing or canceling a money order. Have some faith you will be ok if it is a certified money order
Simon