勉強を見てあげる代わりに、ちょっとお願いがあるんだけど。

、。

I'll help you with your studies, but in exchange I've got a little favor to ask.

Literal

Study [obj-を] see-(give) in-exchange-代わりに, a little favor [subject-が] have (explanatory)-but.

Several pieces. (1) 勉強を見る ('look at someone's studies') is idiomatic for 'help with studies, tutor.' (2) ~代わりに ('in exchange for X') marks a reciprocal trade. (3) お願いがある ('have a favor [to ask]') is the set frame for introducing a request. (4) んだけど stacks んだ (explanatory) + けど (softener/trailing off), a very conversational ending.