[papajam]

Ahh, yes. The infamous side window hinges. Actually, IMO, they're not at all difficult to replace. Approx. an hour per side. To your questions;
1) I've not yet had to replace these. Simply remove what's left of the old hinge and reuse it.
2) only if the current channels are rotted out to the point that they will not longer hold the door gasket.
3) I've had good experience with the Re-Original hinges. No experience with other suppliers but I think that this is one of those parts that isn't critical as far as firmness is concerned.
4) in addition to the visable screws, the sill plates have 'hidden' attaching screws underneath the door gasket requiring the gaskets removal to access them.

Here's a short pictorial on hinge replacement.
Pic 1 - gently pry away the door gasket on the B pillar
Pic 2 - remove three door gasket channel screws and remove the channel. This will reveal the three hinge block screws. Remove these screws to get the clips out. Take note of the location of the screw hole in the clips. The clips need to be installed in they're original location.
Pic 3 - what your old hinge blocks probably look like
Pic 4 - old and new hinges
Slide the new hinges into the window channel. I use an electrical wire pulling lubricant to ease installation. Then slide the clips onto the new hinges.
Pic 5 - ready for installation
Gently install the window into the B pillar and install the three clip screws. Install the door gasket channel using new clay sealant strips if necessary.
Pic 6 - gently install the door gasket into the channel being careful not to 'stretch' the gasket. If the gasket now appears to be too long, DON'T cut it - it's been stretched. Simply remove it and install again.
Good luck!

 

[papajam]

Pics 5 & 6.

 

[papajam]

I may have confused everyone with the use of the word "rubber", ....

I'm no more confused than usual! Besides, it offered me opportunity to finally post the side window hinge pics I took last summer.
Automotive nomenclature can be, at times, challenging in that one word can describe many different parts (rubber), and one part can be called many different names. The door aperature rubber, for example, could also be called a gasket, seal or weatherstripping. Then there's the upright/steering knuckle, boot/trunk, wing/fender.....

 

[papajam]

Exactly right! Not self tapping though, just a flathead Phillips sheet metal screw. Looking a pic and/or dimensions...

 

[papajam]

The only pic I found shows just the heads of the screws. If they are the same screws, and I think they are, as the door gasket channel screws, they are 2.9 x 9.5mm (although that seems a bit on the long side).