Lightroom operates differently than Photoshop or Elements in that it is non-destructive, meaning the order of the operations does not matter, and one cannot build upon the results of the previous, and it does not have layers, so while you can accomplish many things with it, that ways you're used to doing them may need to change.
For example instead of using layer masks to limit where an adjustment is being performed, there are adjustment brushes in LR that limit the adjustment to where you've painted them. There is spot removal which can be used for blemishes so you'll be ok, there. Without knowing what "enhancements" you are performing on the grass and sky, it's hard to say whether you'll be accomplishing the same thing or not.
You can use LR to drive PS7 if you need to still do some things in a destructive, layer-capable bitmap editor; however, if your Photoshop or PSE were current the changes are transferred directly into Photoshop or PSE w/o having to create a PSD or TIF on the way in. With the current LR and an older version of PS or PSE opening from LR will rasterize on the way in instead of just when you save like you can do now.
The noise-reduction and RAW renering are much better in LR3b2 than in LR2 so I'd suggest downloading the LR3 Beta2 from Adobe Labs and give it a try. It expires in June and by that time the released version would be out to coincide with the release of PS CS5, or at least another beta, if CS5 is not quite ready:
There are many tutorials and since LR3 is still in beta, you'd probably want to watch the LR 2.x tutorials and then view the What's New videos for LR3:
http://tv.adobe.com/ is one source of information.
Thank you very much for responding. I've watched a few tutors and I'll watch others. The 'grass' enhancement would be to make the grass a little greener esp if it's early spring or late fall. The 'sky' enhancement would be to make it blue on cloudy days. In PS, it was easy to enhance the sky even thru tree limbs, but, it sounds like in LR I would have to brush each tiny bit of sky.
Usually, you can enhance the sky by using the HSL blue saturation and luminence sliders, assuming it had some level of blue to begin with. If it is neutral gray or completely white, this doesn't work. Grass enhancement is done via the green sliders.
When processing raw files, Elements is limited to the basic tools provided in Adobe Camera Raw.
They don’t even match the ACR tools in CS4.
Lightroom will let you do editing to all file formats on a non-destructive basis without the need for huge tiff documents or PSD files with layers.
Elements has built-in programmed macros which will let you apply filters and effects that CS4 users can only dream of.