Nah dont be scared, just have one file as your editing file and the other as the test file so you can veiw it ingame . Why not try useing filters to add in detail . Like a fabric filter for the hat or a metalic filter for the head phones . The smallest detail counts so look at a photo of the product your making and use it as reference , thats what i do .
I dont use gimp , photoshop is my fancey . I tried gimp and its alot more difficult to me . I'll post a wip of the arm band im working on , pretty much i can change the logo to what ever i want and keep the arm band the same or in different colour .