First, the car. A 1970 Coupe deVille. Now, I'm new to classic cars and motors. All my mechanical/trouble shooting experience is on my '98 Tahoe and friends cars. I've only had the car a couple days so haven't had time to tinker or investigate.

-Issue 1: Lights, head, dash, interior(all of em.) They dim and brighten when the engine is idling or just above idle. It's not a lot but enough to notice. I'm guessing it's a dying alternator(does a 1970 car have an alternator or is it a generator still?.) It goes away as the RPM's climb.

-Issue 2: Wiper don't work. Where is the fuse box? Pretty sure I can handle this one once I know where every thing is located.

-Question 1: Where/What is a good maintenance manual I could buy? I've spent only a couple minutes looking on the internet and the best I found is a Haynes manual that covers all Caddies from 1970 to 1989 or something like that. Any book that general can't be any more helpful than my Tahoe manual.

-Question 2: Where can I purchase an owners manual for my car?

 

Check e-bay for the owners manual and factory service manuals. Some are available on disc, even.
Fuse box is under the dash, driver side, on the firewall.
Lights dimming while idling sounds like a weak alternator(yes it does have an alt), or possibly the belt is loose. Could also be a corroded connection on the alt or battery terminals.
Love them Old Cads!
Ma had a '70 Sedan...huuuuge car! Hood almost took three people to get it up! That's some real American steel!