I'll try I have a tendency not to make lot of sense so here it goes...
the way I did is through hex editing, now I myself am no expert, hell Im not even ok at it. I use hexworkshop
Now on opening the roster file containing your created player you need to locate him and then you have to find the right OFFSET.
Checkout this helpful list of the OFFSETS done by SharksFan and HDK
HERE
There are 100 OFFSETS per player 0-99 so now you need to find OFFSET 93 which is the offset for the wrist tape, now you need to look at the binary down the bottom
ok now im not sure if you will be able to change heads/faces of caps but you can do it through hex
find OFFSET 90
Now i used vunibakas face number 24370 which i found in an xml file
then changed skin and wristbands with woosahs editor
I hope that helps, best thing to do tho is spend a few hours getting to grips with hex