@David A. Jones has explained them.
In addition,我去看=我 马上/等会 去看 （future tense）（would this be easier for you to understand？）
As for 谢谢哦，as a native speaker，I think your friend wants to express his/her thanks more politely or tries to be more friendly. For me，谢谢哦 is more casual than 谢谢，between friends，I tend to use 谢谢哦 to express my thanks, and 谢谢 sometimes can be a little formal. On the other hand, 哦 in 谢谢哦 can be a kind of tone weakening or weak tone, it serves as making formal word(s) less formal.
Hope my explanation help:)