Cam bearing installation... Help please
 

one of my friend took his truck to a mechanic shop here localy for a cam swap but when they tried removing the cam it was sum how hitting the cam bearing. so at the end they ended putting everything together. then after 2-3 weeks he brougth the truck over to the shop for the cam swap and taking care of the cam bearings. ok so we take evrything apart and notice the cam got stuck like 1/4 out... and after messing around with the cam it wouldnt come out and we pulled it out and slip 1 of the cam bearings 2nd to the last and we managed to take it out. so my question is... is there sum kind of way or trick to install the bearings with out removing the engine of the truck. also can i just replace the only bearing it slip off or will i need to install all four bearings.?/?