Just wondering an idea on a Baja conversion to a 72 superbug, Cost? Is it hard to do? should I get it done professionally?

You would have to wreck the s'bug to get the rear end/running gear. Cut the front end off, add an early bug front end and get an early body.

It might be best to buy an irs baja already done, if your not prepared to go from ground up mixing and matching. There are plenty of smart offroaders in/near Brisbane who will point you the right direction. Good luck.