Try it dude,
I imagine you are using the headphones out on your amp. Although the two sockets work at different impedances you should be able to hear something.

AS for recording with an external mic, well the net end result will depend on many things like the type of mic / preamp you use, as well as how you use it.

It probably wont sound much better and may sound much worse !

This is one if the reasons Pods were developed, they are easy to use and sound fine for most applications.