as teckkev has pointed out, you replace the entire boardset, yes. nothing from Blitz 2000 Gold gets reused.
if I'm not mistaken, you can get I wanna say a Gauntlet Dark Legacy (not Legends I don't think, that one might be a Seattle) and swap the video or sound boards (forget which) with the Blitz/Showtime ones and make your own boardset out of those. but on top of that you'd need a security rom/romset/hard drive to run it. you're talking a lot of coin for something like that. ToplessZ is actually going on hiatus for a few months, so if you're doing anything down that road you're gonna have to act quick. ToplessZ has a thread somewhere on here about converting a Gauntlet DL to other games, run a Search on it.
I personally got mine on ebay. they come up periodically. mine was had for $130 before shipping, so it won't murder your wallet if you look in the right place.
I got lucky mine was a 3.0 set, otherwise after ToplessZ's gone, you're gonna have to put yourself in the hands of the ebay people.
good luck, it's an awesome game, the little kids seem to love it in my family's arcade.