Pen marks are really difficult to remove from leather. Sometimes you can get lucky and if it's the right sort of ink and hasn't been there long, alcohol will remove it.I don't have experience rehabbing bags yet. If I just use a surface cleaner then condition my carrier--maybe steering clear of the ink spot--can I leave the ink removal & soaking bath for later, when I know what I'm doing?
Tried removing/lightening pen marks (lines, not an explosion like in my carrier's pocket) using acetone & alcohol on a $3 yellow swing wallet I found. Soaked, bathed & drying now.
Of course it's up you what you do with the Carrier. Is it dirty inside? I like to wash my bags because you never know what's been in them
Personally, I don't like the idea of conditioning dirty leather but that's me. Apparently Leather Therapy brings dirt to the surface where it can be wiped off so it claims to act as both cleaner and a conditioner. I only ever use it after washing so I can't verify this.