Gui Testing can be done on MS-word by following 6 standard
rules  of microsoft.
gui test cases are 
1)proper alignement of the menu and submenu
2)no over lapping of menus
3)equals sizes of all the menu items
Gui testing is done manually 

i dont much regarding performance plz let me know if any one
know this answer

Gui test case explans about the allighment of the 
menus,formt size,appreance and functionalities of the 
objects (ex: If you save a file is it saving) 
Performance testing explans about the load and strees of 
and application

As said, GUI testing is on Menu and Sub menu alignment and 
the correctness in spellings and uniqueness in size of the 
images if any.

Performance Test cases : 
1. Load the Word document to its maximum pages(say more 
than 1000 pages)
2.At this load, Try searching for a phrase in the document 
and check the resposne time.
3. Try to edit some line in the document and save the 
document .check the responsetime to get saved.
4.close and reopen the document and test for its resposne 
time.
5.Try adding some more data to the already loaded document 
and see the response time for the data to get pasted on it.

it continues .....