There is no pin, nor circlip! Clamp carefully the gearbox joint in a vice and pull the gaiter away. Try to pull the driveshaft upwards (like trying to separate the joint). You will notice what holds the joint together: three sheet metal tabs on the tripot housing. you should bend them slightly upwards. The tripot joint will not separate straight upwards, try to dislodge one roller first (by tilting the driveshaft at an angle), then the other two will come off their races easily. Be careful!!! the outer bearing races are free to come off (along with their needle rollers so hold them with one hand.
Now you have the driveshaft with the tripot spider still attached. Wrap some adhesive tape around the spider so as not to lose the three bearings. Remove the circlip, and the spider can be taken off. If no one has dismantlad it before, it will need a three-legged pulled (but not too much effort) to be released.
Now you can remove the inner gaiter, then the outer one.
On reassembly don't forget the spring on the inner joint, and bend back the securing tabs by hitting them with a hammer.
