Just take your docket in to the Service Counter and ask if they can refund the difference... and if they say no, tell them that you'll just go and buy a second one, and refund it with your first docket, which would waste their time and resources processing both transactions.

Someone else was able to get them to do it that way... and even if they still don't budge - if you are able to afford an extra $119, just buy a second one and refund it straight away with your $149 docket.
You shouldn't need to bring in your first Metroplex at all, or worry about repacking it.