Ditto having an honest and open dialog with Dad. I'd add the step of exploring what the replacement would cost and what yours might fetch so you can present dad with a well thought out proposal.

There's also the option of making relatively minor changes to your bike to make it better suited to how you prefer to ride.

You might also five Dad a fair shake here. I doubt his desire was to make you a road cyclist, and instead it wad to make you happy doing something you liked. So an honest discussion about what you like and don't and what you now think would be better will enable the two of you to be comfortable with the change.