Hi Zaid, and welcome to technet,
Hopefully we can get you started in the right direction, but if it's a mission critical application, you might want to hire a consultant for a few hours to help you along. You can find them all over, Elance.com is a popular place.
That being said, here's some recommendations based on your numbered points above.
1, This sounds like you have your relationships set up wrong. In your jobs table, you should have two foreign keys that reference the staff table, one for designer, and one for CS servicing person. You need to relate these two keys to two instances of the staff table, so you can display the related staff person for each position. Then you need a drop down or popup menu of staff, based on two fields (primary key from staff, and staff name), this way when you select a staff member for one of the two key fields in the job table, it stores a foreign key reference to that staff person.
2, this can follow the same relation structure as above. You would just change the foreign key reference to a different person in the staff list. In the staff list you can store a field that denotes whether someone is a manager or not.
3, Filemaker has had "script triggers" for a few versions now. What you could do here is add a trigger to the job assignment field from step 2, and whenever the value changes, run a script that gets the related staff table email address for the new assignment, and run the "send mail" script step, which you can set to send a preformatted email to a designated email address.
These are only basic statements, as I said, you could probably benefit greatly from getting the assistance of a consultant, or taking some up to date filemaker training. Filemaker has indeed changed dramatically in 14 years, and even the past two years.
thanks a lot for your help i think I can do it myself by following your directions. I actually was lost in the scripts now i am back to the track.