Your 5th move is illegal. White already played 3.Nc3. Do you mean 5.Nf3?
Personally, I do not agree with 4...Be7. Not saying it is "bad", it is fine, but after a slightly different move order for White, 1.d4 f5 2.c4 Nf6 3.Nc3 e6 4.Nf3, the best move here is 4...Bb4 and if now 5.Bg5?!, it transposed to your line.
I would suggest looking at 4...Bb4 in your line.
As far as Stonewall vs Classical, the Stonewall is horrible here. Just like how I have mentioned in other posts, 1.d4 f5 2.c4 Nf6 3.Nc3 e6 4.Nf3, the move 4...d5?? Is a blunder as it allows the ideal setup of 5.Bf4 6.e3 and 7.Bd3. Yes, here the Bishop is on g5 and not f4, but it is still outside the pawn chain and can easily return to f4.
My first suggestion would be to look at 4...Bb4. If you cannot do that, like if 3.Nf3 came first and 3...e6 4.Bg5, with no knight on c3, not sure if 4...Bb4+ 5.Nbd2 is good or bad for White. 5.Bd2 loses a tempo and 5.Nc3 transposes. If 4...Be7 is necessary and then 5.Nc3, definitely gotta go with the Classical approach, not the Stonewall approach, but look at 4...Bb4, for certain if 3.Nc3, but also check it out if 3.Nf3 and 4.Bg5?!.
What are the best moves for Black after 1.d4 f5 2.c4 e6 3.Nc3 Nf6 4.Bg5 Be7 5.Nf3 ? I suppose castling is a good and safe idea, but after that ? Would a Stonewall structure still be correct or should we prefer a kind of classical variation including d6, b6 and Bb7 ?
Many players use this line, and they sometimes castle on Queen's side ! In such positions I don't think the LS-bishop is well placed on b7.