Soak steel wool in a jar of vinegar for a day or two. Then, put that concoction over any type of unfinished wood. Some type of chemical reaction happens (Science isn't my thing) to give it an aged look. To further age it, beat the heck out of the wood w/ a hammer or any old object laying around, drop the wood, kick it, etc. You can also use a dry brush to lightly add "old paint" to it.

A more labor intensive way to age wood would be to think about all the finishes it would've had if it were genuinely 50 years old. It would've been sanded & stained first.  Then, banged up A LOT & when it was good and banged up someone would've primed then painted it. Then over the years it would've been painted & repainted.  And finally, it would've been banged up more with a lot of wear on the edges, around knobs, etc.  So follow that pattern--sand it, stain it, beat it up, prime it, paint it, paint it, paint it, paint it, beat it up, use a sander to add wear to commonly touched areas & edges.  

You'll want to find a dresser or cupboard that is bench height or a dresser that has legs. Legs are easy to remove (they generally just unscrew--those are the easiest). Remove the legs & you have a bench height furniture piece.
Here are a few BEFORE pictures of good starting pieces...

Remove old hardware & prime & paint the piece.

Cut a piece of plywood the same size as the existing top of the bench. Then, spray glue padding & a layer of batting to the top.  Finally, use a staple gun to upholster the top.  Here is a great tutorial from The Little Green Notebook on upholstering a bench top & on how to do the corners (which can be tricky) UPHOLSTERING A BENCH TOP + CORNERS

After the top is upholstered, position it on top of the piece's existing top, remove the drawers (or open the cupboards) & screw it in from the underside/inside with screws long enough to go through both layers, but short enough not to poke through your upholstered bench top.