Fender Sidekick Reverb 30

I very rarely play out, and when I do its at a jam, so I don't bring my amp.  This amp was given to me about 20 years ago, and I don't use it that much.  The controls are Volume, Master, Treble, Middle, Bass, a broken knob labeled Presence, and Reverb.  My mike is a Hohner Blues Blaster, which I gather isn't a very good mike.

Is this amp any good for harp?  Where can I get a knob to fix the Presence control, and what does "Presence" do?

Any suggestions on a new mike?

Thanks!

Phil