I am just starting out with modeling in blender and I am making hand guns mostly. I am wondering if mirroring is the best way to go when working. If I use a mirror, I am restricted to the x and y axis in terms of being able to move the model around. Is there anyway to make an object with a mirror and then get rid of it later on without losing the other side?

Do you mean the mirror-modifier ? Then yes, it is often the best and fastest way to start with mirror modelling. If you want to add some asymmetrically features you can just add it as separate model. Later on, you can "apply" the modifier, that will remove the mirror-modifier and the mirrored vertices are added to the model. Best to keep the mirror modifier as long as possible. It is even possible that, when exporting your model, that all modifiers are automatically applied.

What about something like a shell ejection port on a gun? I would use the mirror first, then apply the modifier, and then put the ejection port on the proper side, correct?

Yep, this would work, thought if it is possible to separate this part of the model, then I would keep the mirrored part as long as possible. Applying fixes to the models once you have applied the modifier will be harder. You can stich the model together later.

best thing to do is make sure you save a copy just before you apply the mirror modifier and begin your non-mirrored modeling. that way you can go back if you mess up.

generally speaking, the usual approach seems to be to model things mirrored as much as possible (to reduce work and preserve symmetry), then do the non-mirrored modeling of the object.

keeping a copy of the mirrored version of all models might be wise, as you'll be able to go back and change them later with greater ease. Once you apply a mirror and start non-mirrored modeling, it can be hard to go back to the mirrored state.

Moving this topic to Visual Arts.