Trans pan gasket..sealer or no sealer?? and other trans ???

OK all, I'm looking for some informed opinions about this subject. I am doing a trans filter and gasket change on the 66 convertible and I am going to use the gasket that came in the filter/gasket package. Should I use any sealer on the gasket before I put it back together??

A little background... When I got the car and drove it up on the trailer, the trans was "squealing", making a noise that sounded like a band slipping or something. I drove it off the trailer and around the block, and when pushed it would squeal, but shifted through the gears under light pressure without making a noise. I figured a filter and gasket change would be in order to remove any burnt fluid and see whats going on in there. I am not sure this is going to fix that squealing, and may have to go back in for what?? I don't know. I'm not a trans guy and am not sure if any adjustment is done inside the pan and don't want to seal it up and have to go right back in, hence my question. I guess if anybody can shed some light on the adjustment of the bands also that would be a great help. There looks to be an adjustment inside the pan and I'm not sure what it adjusts.

Also, I'd like to get any opinions on what trans fluid everybody is using for these old cars. I hear a lot of people are using the old type "F" fluid and to stay away from Dextron. Any help would be greatly appreciated. Thanks all for your time!!! Geof