call to gauge prices , it is your local area so only you know who you would go to ,so get their prices .
Also if it softens when the a./c is on at a stop it isn;t crazy as a problem as the a/c kicks inthe throttle is closed but the rpms raise to compensate for the drag on the engine. So you will end up with more vacume causing the pedal to sink slightly.
Check the idle control valve also as it can cause idle vacume problems also if diagnoised properly.