Haven't seen the panel yet, but assumming it does have room. The spa probably does have a GFI built into it. Can get a 50a GFI for the panel at HD for around $70 to $80.
I will have to buy the disc, about $20.
Will I need a GFI recept within so many feet of the spa? Guess I better check the code book.

The Golden Rule - "The man with the gold makes the rule"