Update

So, I've done some more planning, with Do Hyun and his brother (whose name I never remember)... It was really encouraging. We looked at maps online and the maps that I had and have come up with this as a route. For the most part, I will be following 2-lane country roads that go along the 4-lane National Road 2. The entire distance is roughly 150 km (from Shidae apartments to the Mokpo Bus Terminal), and I should be able to do it in way less than 5 hours, but I still want to give myself ample time to do it and explore etc. I did the first leg of the trip last Sunday afternoon, and it is hardly like going through outer Mongolia. Anyway, here's the route:

Suncheon
Nagan
Beolgyo
Joseong
Yedang
Boseong
Jangdong
Jangheung
Gangjin
Seongcheon
Dokcheon
Mokpo

And, I have phone numbers and contact names of bike shops at two different points along the route. The only thing that will change anything now is the weather. It's supposed to rain on Saturday, which may cause the whole trip to be postponed.