Hi Chan,
I just completed the task of replacing the guides on the driver's side window. I pretty much followed the procedure in the wiki. I think you'll find that taking the window out is not too difficult and will make the proper placement of the guide and felt a LOT easier.
One thing I did find, is that you want to use a very thin layer of epoxy to glue the felt onto the window glass (as well as fairly thin felt). There is not a lot of clearance between the aluminum guide and the glass. I had to shave the felt down with a single edge razor blade to get a good (and not too tight) fit.
Since you've already got the door panel off, removing the attachment screws for the glass is not a lot of work. Just be sure to support the glass while removing the attachment screws. As I remember, the glass is sandwiched between two pieces of support metal...there is not a channel that it sits in so the glass can fall if you don't support it.
Good luck and as always with these "little" projects....take your time.
Richard