Jens Gunderson Aas of Gjerpen Skien Telemark?

Hello all; One of my ancestors was Jens Gunderson (Aas) from Gjerpen. The family information I have relates that he was one of the first emigrants from the Gjerpen area in 1850, and moved to Wisconsin. We are traveling to Skien in early August and I would love to see the Aas farm, as well as the farms of other ancestors including: Meen, Stulen, Fjelldalen, Gulset, Kleven, and the Fossum Ironworks. We'd also love to see the Gjerpen church. I haven't had much luck getting in touch with people directly, so I'm hoping that you all might be able to help . . . thanks in advance! Liz