The baby gate is exactly what I was going to suggest. Remember they can jump the gate, so you want to watch them.
Just take it slow. Don't leave them out together while you are gone until you are sure they get along fine.
Let them mingle while you can supervise them. Don't jump and put Murphy away if Nugget hisses. Let them work it out (unless they get into serious fighting, of course).
There will be hissing and maybe even a swat or two. That's normal.