Although your window switches may be up to snuff, the relays might not be. They're located behind the center console... I would pull 'em and re-solder 'em.

I'll take a stab at the window problem. From your description, it sounds like a lubrication problem with the regulator mechanism and/or the channels the glass moves in. I have been able to make the windows in my 940 work much faster after putting spray grease into all the regulator pivot and slide points. Then I sprayed silicone lube into the channels several times while running the window up and down. I haven't had electric windows in any of my 240s but I have lubed the manual windows in all of them with good results. Just be careful not to get grease on the glass or it will take forever to get it out. Lube the lock mechanism while you are in there.

Also check the bolts holding the window motors. These can loosen and give problems.

Another warning. The inside door panel in an '84 may have deteriorated from moisture and may even be crumbling. I had to go look for a used but solid panel in a pick-and-pull yard for my '86 240. The PO had left out the water shield which protects the panel and the panel had a very interesting mold ecosystem growing on it.

Welcome.

Yes its quit a bit of work to replace the blower motor, take a look here and see what's involved:

http://users.erols.com/benstein/

Also take a look at the FAQ section of this site.

You may also want to pickup the Bentley service manaual if you will be working on the car yourself.

I can't help you with the power window problem. I owned a 245 that developed window quirks after a while, and no one here or anywhere else could tell me why. I could correlate the problem with temperature differentials, but could never figure out why. Then again, where I live, I hardly need to open the windows anyway.

About the blower motor. Most likely the motor is toast. You correctly note that it is not easy to get to. Volumes of blower motor lore exist here in the archives. Good luck.