If the fuel injection pressure regulator is leaking; there are two ways it can be fixed. One would be to replace the regulator (for the 2.2 liter 4 cyl, this part costs $42-$58 at Rock Auto, depending on brand. It will cost more locally; and a mechanic will typically mark the price up an additional 40-100%). The other way to fix a leaking 2.2 engine's regulator would be to install a new fuel injection pressure regulator seal kit (AC Delco part # 12574284). This part costs $16.52.
If you have the 3.4 liter V-6; a new pressure regulator costs $44-68 at Rock Auto; and there is no seal kit available as a lower cost option.
The regulator is held on by a single bolt and a tube fitting. There is one vacuum hose that is also attached. It is a simple, straightforward task to replace it. But you will need wrenches which properly fit the fasteners.
Since labor and mark up rates vary considerably in different parts of the country; it is not practical to try to give you a price quote. If you phone a local shop and ask them what the flat rate time estimate is for replacing the Fuel Injection pressure regulator; they will give you the number of hours (or fractions of an hour) that are normally charged when a professional mechanic does that job. You can then multiply the time estimate by the shops' hourly labor rate to get the price.
But it is sometimes risky to go on the assumption that your car has the same problem as other cars you have heard about. You might end up paying for parts that are not needed; and which don't fix the problem. One way you can determine whether it is the regulator is to pull the vacuum hose off and see if it has fuel in it. If there is fuel in the vacuum hose; the regulator is defective. If there is no fuel in the vacuum hose; the problem on your car is somewhere else.
Look up your car's brand, year, and model on Rock Auto's website to see a photo of the regulator. It is in the fuel/air category. Click on the blue icon with the "i" in it after the part number, to see a large image of the part.