오랜만에 타 본다 -> It's the verb 보다 right ? In the meaning "to try", isn't it ? So I could translate it as "It's been a while since I tried". But why is there a ㄴ in 본다?
‘보다’ in Korean functions as a main verb, an auxiliary verb and an auxiliary adjective.
-나는 나무를 보았다.
-먹어 봤어, 입어 봐라, 타 보다: try or experience
-저 사람 가수인가 봐. guess
-When you want to impart your emotional feeling to the present event, you can express that with your voice tone(exciting or wistful) or with a new vocabulary. If you say the sentence "오랜만에 탄다“ like a news anchor, it is only about the fact. If you say that with a Yves Montand's tone, you are brushing your emotion over the fact. If you are a more expressive person, you can add a new vocabulary to the fact and voice tone. Then you get a painting rich in colours, touches and composition.
-오랜만에 타 본다. (So long both objectively and psychologically that it is almost like the first try in my life.)
얼마 만에 = 얼마 동안 ? Can we replace one by another?
-'동안‘ is about the duration of time.
-‘만‘ implies that certain amount of time passed.
-지하철역까지 얼마 동안 걸었어? 1시간 동안.(O). 1시간 만에.(X)
-(집에서 출발하여) 얼마 만에 역에 도착했어? 1시간 만에.(O) 1시간 동안.(X)
Could you say 서울 살면서 in written sentence or is it only oral speaking ?
Yes, but almost.
You can write that way in e-mail, diary, texting, or enjoying your own Pensées.
Not in any official documents.