If I do it, are there any risks of a Google penalty?
Also, if I do it, should i build a site on the expired domain? I could build a small site that directly relates to my blog. I can't find info on this, most things simply talk about 301'ing the domain itself. (I'm not even clear if that's possible as never tried it)
I don't want any of the expired domain to get indexed as I do not want the name to show anywhere.