New Ferret Friend for my Ferret

Question
I'll start by saying that I had two male ferrets that were the same in age (around 4 years or a little older) and were definitely buddies, but a few weeks ago one of my ferrets passed away. My other ferret seemed to take it okay as he continued to eat but maybe I guess you can say he maybe moped around a little.

About a week or so later I got another ferret so he could have another playmate and someone to cuddle with when asleep. I got a female whose previous owner says she is close to 3 years old but I'm not quite sure if that is true or not. They don't fight all the time but I have to supervise them at play and I keep them in seperate cages when I'm not around. My question is, was it too soon to introduce another ferret and if so for the health of my older ferret should I try to rehome the one I just got or just keep doing what I'm doing (keeping them in seperate cages and allowing them to play supervised in hopes they will bond eventually).

I just don't want to stress out my older guy as I have read that that can cause health problems. He seems to hide sometimes when the female comes at him face to face and he backs off, but other times he chases and plays with her just fine. Today though I think he wanted to show his dominance as he attacked the back of her neck and she squeaked her dislike pretty loud and tried to attack him back and hissed when I broke it up. He's probably twice her size so I was afraid he would do some serious damage to her. She also does the same to him sometimes.

Answer
It sounds like they are getting along just fine.  It can be hard for us to watch and listen to ferret interact like that, but it is common and pretty safe.  I would really keep them together as keeping them separate can intensify the "issues" where as keeping them together allows them to work it out.  Since no one is getting hurt and each backs off when necessary, they will be fine.