1. I doubt it, but that totally depends on how handy you are.
2. Just say "it's been making a hell of a squeaking noise when the furnace turns on" and let him figue it out.
3. Sorry, I live in Nova Scotia so I can't help you here.
4. Hard to say, it depends of what those shitheads charge for walking in the door. Changing the belt is easy for them but hard for someone who isn't too "handy" so it should take him about a half an hour. However, if you have a bearing problem, that's a whole 'nother story. I highly doubt you have a "pulley" problem. I also highly doubt you need a whole new unit.
5. While it's probably not an emergency, you should get it done ASAP.

I had a similar problem with my furnace. The blower had some real shitty design for a bearing with disintegrated and the shaft came out of it and wore a slot into the blower housing while it made a hell of a sqeaking noise. It completely ruined the shaft.

So, I contact some HVAC parts place and they tell me it will take a month to get a shaft and six weeks to get the factory bearings (which were no fucking good in the first place). So my brother found some shaft stock from someplace (my brother works for a steel company and knows shit like this ) and made our own damn shaft and we did some research on what better design of bearing would work in this particular housing. We had the thing fixed in one day.

Now even your most trained furnace "professional" wouldn't have the first clue to do know what to do in my case instead, he'd have you waiting two months for parts...