the folks here appreciate this and thank you:-)
well, to summarize this a bit, we´ve had a few tips here:
1) Just outside Gwangjang Market
2) Hwanggu restaurant on the outskirts
3) some "cheaper places" in Jongno (any exact known?)
4) asking for "kay-go-gi" or "bosintang"("s" or "sh" spoken/written there?), probably in the info booth on the Sejong-daero avenue, where they had a good english last time.

Which one would you, local (or half-local) guys suggest to a lonely traveller, wanting to just taste a dog with the priorities:
1) sureness of a dog meat
2) good price/power ratio
3) easy access by the public transport from icn/gmp/city center (t-money already in possesion)?
Thank you for your cooperation and feedback!