seals will be still available from yamaha i think
although i have never done it this way, you drill two very small holes into the front face of the seals 180 degrees apart, then screw in some appropriately sized self tapping screws and pull on the screws to remove the seals,
A few other things to consider...
You will need a flywheel puller, dont be trying with a 'legged' type, and smething to hold the engine solid while you both undo and torque up the flywheel nut, I use a chain type filter wrench and some rubber strips
For the right seal you will need to lock the engine from turning so you can undo and re-torque the pinion nut, on this side I use a clutch tool but in the past i have removed the cylinder and passed a bar (socket extension) through the small end onto wooden blocks either side of the con-rod. Also for the RH seal you will find a spacer collar behind the pinion, it slides on the cranshaft and enters the seal, this collar is sealed to the crank by an O ring so buy one of those too
I wouldnt advise holding the opposite side of the crank to the nut/bolt you are working on
of course doing it the lazy way (and who could blame you) assumes your crank bearings are in great shape
Have you a parts list Jim?
Again...what of the spark issue!