Customization of OrangeHRM

I require small changes to be made to a OrangeHRM installation. The programmer would have preferably worked on OrangeHR before. Here are the changes required: 1) be able to select days off for staff so that if a staff member has a Tuesday off (i.e. because they are part time), when they book mon to wed then it only allocates 2 days. 2) be able to make sure that 2 staff members fromn the same dept cannot be off together. 3) ensure that once a holiday has been approved/declined then the staff member gets an email 4) have a calender view (if possible)