I just bought my first home this past February which needed a bit of updating. The house was built in 1964 and is mostly all original. Besides the basics, I've redone the kitchen myself (new tile floor, new cabinet doors/drawers and sprayed cabinets)....My house is built on a concrete slab and I'm right near the water on the south shore of Long Island with many canals/etc. in the area.

The second floor of my house is the original hardwood from 1964 which I'm guessing is Oak with a clear/natural finish? It is a 2 1/4" wide plank...The first floor entryway currently has slab tiles leading into ugly blue carpet. I'd like to rip up both floors and put down hardwood in the entire area.

After some research, it seems like engineered hardwood would be my best bet. I'd like to go right over the slab to keep the height down. Any and all help & recommendations to a newbie would be appreciated...

Are there any brands that I should try to stick with?
What do you think about some of the lines that Lowes carries such as Bruce, Natural Floors by USFloors, etc?
What about Lumber Liquidators Schon, Mayflower, Virginia Mill Works?
What type of underlayment should I go with over the concrete slab?
A lock type floor seems like my best bet and user friendly over the slab, correct?

Yes engineered
Yes to Bruce and especially USFloors
No to LL or any of their products especially close-outs = seconds
Some locking engineered has squeaks, try Mirage, I had good luck with one of theirs. Always look up reviews on the net.