ok ive been at this for ages im trying to retexture the stock diary with one of my own but i just cant seem to get it done can someone help

Wooah, wooah, slow down there! What can't you seem to get done? Are you having problems finding the diary in OBJ workshop? Can't find the texture?

sorry i should have explained better
ive found the texture(i think) using SimPE and edited the texture but then its getting that texture to replace the stock texture ingame

I believe it's a more involved process than just changing the texture. Because it's not a stand-alone object, but part of another (the bookcase), you're probably going to have to clone it and replace the old GUID references to the new ones. Echo's written a great tutorial on fixing self-referencing objects here.

Good luck!

megas - are you trying to create an override for all diaries in the game, or are you trying to make an alternative diary for one particular bookshelf?