np203 question on gasket replacement

[Cornfield creations]

I got my chain housing to selector housing gasket for my 203, it started leaking after sitting for awhile. I was wondering on procedure on replacement. It is in the blazer yet, hoping that helps some.

I was told to be careful because there are a lot of needle bearings that like to fall out when separated. Thats all I know as of right now. Thanks in advance!

 

[Cornfield creations]

would it be possible to unbolt the chain housing from the selector housing while in the truck, and slide it apart?