While I don't have information on this Gassen branch, I have done research on another Gassen family from Kaltenreiffersheid [that's "kalt" as in cold]. The town name is now just "Reifferscheid" in the Andenau region [use Google]. There's another Reifferschied not too far away called Reifferscheid bei Hellenthal. I found my Gassens listed in those records too in an FHL/IGI search online.
The Family History Library films were very helpful for my research and I remember the name Claesgens in the records too. Even if you don't know any German, you can find a library book on German genealogy that includes alphabet charts of the old script as a reference [a good starter book is "Discovering Your German Ancestors", by Thode and Anderson], where you can also pick up the mandatory, but basic German vocabulary that you'll find in the church records. Whether they're in German, English, or Latin, etc. the church records [Catholic or Protestant] use standard phrases for recording baptisms, marriages, and deaths. And many times you'll find the records easier to read than later local church records for your family.
I hope this is helpful to you. You can find my Gassen ancestors posted on Rootsweb.