Hi
The starter is a motor that spins the engine until it can run by
itself. Did your mechanic replace the starter, while the engine was
turning over? If the car 'turns over' (i.e. you hear the engine
turning), the starter is just fine.

If you have to press the gas to make it start, it could be that the car
is flooded.
It could be that you're not getting a hot spark - check when the
distributor cap, rotor, wires and plugs were replaced. These items
could easily do what you are describing -- you can easily replace these
things yourself.

Hope this helps you.
Remco