Hey Man,
I am a worrier like you, and actually changing my starter clutch somehow turned into a complete rebuild, frame powder-coating, engine overhaul etc..., so perhaps my story isn't entirely the correct advice, but as to spending a fortune on tools, as people said here already, you can get away with alot.
Using the brakes, or a well padded chunk of 2x4 inserted through the wheel, and wedged against the swingarm does wonders. A good breaker bar is cheaper than a good impact, and in a pinch, a length of pipe over the end of a regular ratchet does the job, and is very cheap. As far as bearing drivers and the like, ABS and PVC pipe are great for the task as they can be beaten on pretty well, and still not mark up or dent bearing surfaces. A quick trip to the hardware store/plumbing dept with your bearing, or the measurements and a cheap digital set of calipers should produce SOMETHING that will work quick enough. If it is a hair big, sand it down, easy enough.
Never though of turning a whole bike upside down like that to do a started clutch, but it sure would make it a pile easier! Might even be able to get away with NOT removing the exhaust system. All that being said, I did flip my motor upside down to do mine, Made it far easier, but it wouldn't have been too hard elseways. Honestly, I think if I had to do it again, I would at least attempt doing it with the motor in the frame etc.... The directions did make it seem like it would be a good deal more difficult than it ended up being.
Cheers, and good luck!
Jon