Hi and congrats!!! what a pleasant surprise for you!
I'll try to answer your questions:
1. What is the best tank temp. for incubating the eggs? I'm afraid that my tank is too cool. (like 60-65) I have a 10 gal. tank.
it's quite ok, but try increasing it to 68-70
2. The eggs have been laid for about 4 days, and there is one little whitish speck in all of them. What is that???
it might be fungus. if it's a black speck it's the fry's eyes. if u see the whitish egg growing fuzzy, take it out.
3. Will my goldfish do this again sometime? The fish I think is the female still is round/chubby-looking.
they might
4. What do I DO with all these baby goldfish after they hatch?!?!?! (If they do hatch that is....)
let them be for about a few days. they'll stick to the walls, digesting their yolk sacs, then after that they'll go free swimming. once they're free swimming immediately feed them crushed egg yolk or baby brine shrimp if u can. liquifry is also ok.
PS : maybe it's better to set up a spare tank or a bucket for the fries. makes it easier for u to clean and they wont be disturbed by the older goldies
hope that helps
edit: gaah tazz knight beat me