The turbo trans is a Gtype not an F-type.
ATF is the fluid installed by the factory in both G and Ftypes. It should not have cause the trans to implode, it's not ideal but many Capri live their whole lives on ATF.
The shifter seal is a bummer. I think the trans needs to be split apart to replace that seal.
Could possibly cut off the shifter connection, pull out the old seal, install a new one, and carefully re-weld it