Again, good job! Clever that you created home plate facing the right correction.
As to the shadow, don't do the stroke. That just adds an unnecessary step and might even wipe out fine detail in the shadow.
Here are 2 ways:
1. Ctrl-click the object in the layers palette to select it. You will see "marching ants" around the object, indicating the selection. Fill the selection with black.
2. On the layers palette there is a "lock" icon, which locks transparent pixels. Click this and fill the layer with black. There is no need to first select the object since the transparent portion will not be filled. In my ancient PSE2 the lock button is at the top of the palette. In PSE9 it might be somewhere else in he palette (maybe on each layer?).
The Opacity slider is also on the palette.

While I'm at it, here is how you could add baseballs.
Go a Google image search on "basebalI". This brings up a zillion hits, but we want a baseball with transparent background.
Click the Options icon in the upper right corner and select Advanced search

Choose an image size close to your picture's size.
Choose type of image, Photo in this example.
Choose file type PNG. PNG files in Google images should (but not always) have the transparent background.

Click on a baseball you like, to enlarge it. If it shows the transparent background, right-click the image to save it to your PC.

Then add the baseball to your picture, resizing and re-positioning it as necessary.
