nice work, it is the big liver journal.
fellowships are of course looking at what publications you have, but more than anything they want to see that you're legitimately interested in the field. If you're the third author on a paper as an undergrad, great, but if you don't care to do anything else all the way through med school and residency (7 years) people are going to wonder if you really want anything out of GI, and if you're giong to do anything while you're at their fellowship. If you keep working on extracurricular GI-related papers through the next 7 yrs, then the sky is really the limit in terms of what fellowship you go to. Do more, be a first author, and begin to think for yourself and design some papers. Programs want people who are active and think outside the boax, and thereby change the way things are done, change the field itself.
Why GI? You haven't even started med school. It's very rare that people know what they want before med school even begins. Often opinions keep changing even through residency. Nevertheless, you're already working w a very active group, so don't cut any ties now. The type of work you're doing now looks great for any area of medicine you apply, and will keep you disciplined as school gets more intense so you'll still be used to doing some extracurricular work.
The incomes of fields are always changing, don't choose GI b/c it's currently lucrative. First and foremost, choose fields that keep you interested.
