Is Seoul like Tokyo but less extreme and more conservative?

i would start with the classics .. like "do's and dont's in Korea", usually sold in airports and malls.

You really have to be careful with comparing cities, and especially framing one city with reference to another. I mean if you go to Seoul looking for "Tokyo" you're setting yourself up to fail. How can Seoul be more "Tokyo" than Tokyo was? Instant disappointment.
I learned this the hard way. I moved from Tokyo to Seoul and spent a year bitching about how Myeungdong was a low-rent Shibuya/ Harajuku was cooler than Garogusil etc etc When I left though, I found surprisingly I missed a lot of things in Seoul I hadn't appreciated when I was there.
Its the easiest trap in the world to fall into, but you really have to try and avoid it. Go to Seoul with an open mind and see what strikes you, or just - go back to Tokyo if you know thats what you want. My advice, anyway.
I agree with much of earlytorise's assessment. Seoul is a bit rougher around the edges, but also a bit less clinical than Tokyo. It is not as refined, more red-blooded. There is good and bad to that. In terms of fashion, Tokyo wins hands down. In terms of food or nightlife - I prefer Seoul.

PS -oh, and Seoul is much more conservative, yes.