Objects automatically join

Hi there

Noob alert: I use Blender 2.71. I am trying to make a cartoony cow (very shawn the sheep/wallace and grommit style), and I have a couple of questions.

First (most important) question: After I make a very basic head shape I try to add the eyes using UV spheres. However, after I placed the eyes inside the head, as soon as I deselect the spheres they somehow become a part of the whole head, so I cannot select them separately again. Probably just stupidity on my side, but can someone please help me with this?

Second question: If I want to texture my cow, is it really necessary for it to be symmetrical for me to effectively UV unwrap it? On all the youtube tutorials I see they always have a mirror modifier on their models. eg, If I want one horn to be kinda skew, or one eye slightly bigger than the other, will that mess up my unwrap?

Thank you!

If you add an object while in object mode it will be its own separate object
If you add an object in edit mode it will be part of the object you have in edit mode.

To separate a selection of verices into its own seperate object, select the vertices (use Ctrl+L to select linked vertices) and press P in edit mode

If I want to texture my cow, is it really necessary for it to be symmetrical for me to effectively UV unwrap it?
No

If I want one horn to be kinda skew, or one eye slightly bigger than the other, will that mess up my unwrap?
With the modifier enabled, unwrap, apply the modifier and then make your adjustments to one side

Ah thank you!