One of the nice things about Photoshop is there is usually more than one way to solve a given problem.
(A) You didn't mention it, but if your logo text is by chance all black, changing the layer blend mode from Normal to either Darken or Multiply will neutralize the white.
(B) In the more likely event where it's not all black or is multicolored, try this:
* Turn off all layers except the logo on white layer
* Open the Channels Palette (Window > Channels)
* While holding down the Ctrl key, click the RGB channel. This will (what's known as) "load the selection." "Marching ants" will appear around the logo, selecting the white area.)
* Back to the Layers Palette
* Select > Inverse (selects the logo instead of the white)
* Layer > New > Layer via copy. (This will create a new layer from the selected logo without the surrounding white.)
Turn off the original (with white background) layer so logo-only layer is visible. You may have to duplicate this layer 2-3 times in case there was some loss of opacity. Merge the visible layers if this is the case.
Now you've got your logo on a layer with a transparent background. You can fiddle with opacity, layer blend mode, add Layer Styles, whatever you like.
If you want to change text color, while holding down the Alt key, Layer > New Adjustment Layer > Hue Saturation. Click the "group with previous" (or "clip" if you have CS) option and then OK in the New Layer dialog.
In the Hue Saturation dialog:
* Turn on option Colorize
* Set Saturation to + 100 and experiment with the Hue and Lightness controls.
Does this help?
re:
Why don't they make a more user-friendly index and complete manual? Yes, I think I know. Adobe wants to sell its technical help services at $29.50 a pop.
My opinion:
Trying to document all the things Photoshop can do would be impossible, even if they seem relatively easy. There's just no end to the possibilities, option combinations, etc.
Making a more comprehensive manual would cost them more money = less profit and we know profit is the end objective.
I don't believe they're necessarily trying to get people to use their fee-based tech services because they realize there are so many free and effective online forums like this one, including ones they offer at Adobe.com.
Some customers prefer to "talk" with live humans vs. use a venue like this for assistance, so the service Adobe offers meets the needs of folks falling into this category. Consider that not everyone is as brave as you when it comes to hanging out their dirty laundry in public (that is, admitting "I don't know how to do X. I need HELP!"), nor has the ability and/or confidence to put their situation into words as well as you did.
re:
Thank goodness for this forum...
Ya got that right.
~Danny~