Hi David and welcome to TRS~!
You mean the connector on the transmission won't come off?
If so, it is a common problem that is easy enough to fix usually...but it takes a bit of manual dexterity.
The slave fitting is a coupled connection and it usually comes apart by pressing the ring on the back side backwards and pulling the hose out in the opposite direction. When this fails it is usually because the plastic ring that compresses the fingers in the connector to release the hose is not moving with the outer section as it should.
To correct this you can try to push the white plastic ring back over the fingers using two slot head screw drivers or similarly shaped tools (Ford actually has a tool for this). I made up a tool like the Ford one out of an old bicycle wrench and it worked a bit better because that frees up one hand so you can use it to pull the hose out of the slave fitting.
Note: It also helps if you PUSH the hose into the slave while working the ring connection back. I think this has to do with the pressure inside the hose from the fluid but not sure...but it does actually help.
The tool was just a 1" or so wrench that fits the plastic ring. I'm surprised nobody has made a Tech article for this because it is pretty common. The first time I did it I tried the two screw drivers and it worked...eventually...
I hope this makes sense...and is what you are looking for...
Another option would be to cut the hose and fit it with a pressure fitting as one mechanic did to mine years ago. I think I still have the fitting. Since you are replacing the master it will need to be bled again so not as big a deal for using this method...
And the third option is to knock out the roll pin that holds the hose to the master and then put it back on once the new master is bled. This requires very good manual dexterity because you are working under the hood and may not have much room to do anything...but I did this once...only I had the 2.3 so there was more room to work.
Replacing the master requires the above step whether you do it under the hood or on a bench...on the bench is obviously easier!