> "2) I hear alot of overseeding.... What is that all about? "

Over seeding is additional seeding OVER an existing, established lawn, once it has become older and tired and needs to be replenished. Think hair plugs and grafts on a bald or thin head ... like me, LOL!

That's not the case with new sod, which is still very young and very capable of recuperating from injury like a child does.

Fall is the best time to fertilize. Try to do it at least twice ... oh say Labor Day and Halloween.

Fall IMHO is the best time to kill weeds. Common weeds like dandelions, are winter annuals.
Kill them now and you don't see them next spring.

I would fertilize it with a high nitrogen fertilizer (something like 21-0-0 or 46-0-0), using enough to apply 1 lb of actual N per 1000 sq ft after the top growth has stopped but while the grass is still green. The exact timing of that will vary depending on your conditions, which is why I don't try to tell a date.

I wouldn't overseed. That grass should spread to fill in any bare or thin spots.

Looks like Gary and I hit submit about the same time.

I agree that fertilizing twice in the fall is usually a good idea, but I think the last one is the most important one, and it may be too late to do two of them, so I only suggested the last one. Next year, fertilize once in late spring (after the first flush of growth is past and before it starts getting too hot) and twice in the fall.