No, you don't need to take the engine out and remove the crankshaft to change the upper half of the seal. And, yes, you can change it using the various methods described, with or without removing the transmission. The oil/lubriplate/grease suggestions are good ones that will help the process, and packing it as described by Hotrod Lincoln was common practice. Lowering the crankshaft a little is the critical part of the exercise. The reason Chevrolet manuals show removing crankshaft is that the required 'seal installation tool' is a driver that looks rather like a hammer that you use to seat the seal in the groove. I don't recall ever seeing anyone use that tool, even if the crankshaft was out of the block. The installer tool was part of the 'Essential Tools' kit for Chevrolet shops, and probably also for GMC shops. Chevrolet shop manuals show using installer tool. If I can find a picture of one, I'll see if I can post it- just for amusement.
Harvester
