1) Good job posting your specs
2) Asterisk add-ons merely installs extra asterisk modules. More modules being available is not likely to disrupt things unless they overwrite an existing module (vicidial customized and installed?) that happens to have the same name.
3) VMware / vSphere / Virtualbox are all great methods to experiment with such things. All free. All capable of at least one call using the exact same configuration/files/setup as your live server. And if you break something in what was once a working system in one of the virtual systems ... there's a reset button if you can't figure it out (so you can try again!). Just remember that it's not reliable for more than testing with a single agent, and you're all good.