I am extremely pleased with WR time tracker after i had hard time installing it

I need to make some editing in it. and it will be great if some one can guide me through this:
1- i want to change Weekends days to Sunday and Monday
2- i want to remove people, clients, Projects, and Activities banner links from normal user view.
3- I want to remove 'Billable' check box
4- in the time sheet, i just want to keep duration. i want to remove start and finish time
is it possible to do this from the PHP Code? I don't know PHP. but i can follow instructions and do miracles

Regards
Hosam