Thing is, bikes don't hold on to their value very well.
If Dad bought the bike new from a shop, selling at half the purchase price is common, even at very lightly used, nearly new bikes.
At the very best, you might get 75% of the original purchase price. Possibly, if you still have the receipt so that the next guy can benefit from the remaining warranty.


So if you're looking to sell and buy, the new bike will be considerably cheaper(and cruder) than your current bike.


Don't know what you mean by "play with", but there are certainly things you can do to make a road bike "more mellow" WRT riding position, but you can't really sensibly turn it into a cruiser or a BMX.