That should be easy to change a five gallon tank. Get a five gallon bucket, transfer four gallons of tank water over with the fish, then get a pair of pantyhose and stick some old gravel inside (to help transfer the bacteria) and stick that in the bucket. Then clean out the tank totally and set it up like you want it, then transfer everything in the bucket back over to the new tank and keep the old gravel in the nylons as set it in there as well. You may have to top off since you will have lost about a gallon, but that is similar to a pwc amount anyways.
If you plan accordingly, you should be able to do the entire process in less than an hour.
(BTW, I think the planted tanks you have seen have been ecocomplete gravel which has nutrients in it to help plants, not just plain black gravel - but you probably already know that)