I have a 1998 Pontiac Firebird V6 and I need a new fuel pump for it.

Check rockauto. Com. They will have listings for many suppliers. Be aware that many suppliers buy them from the same manufacturer. Case in point, NAPA fuel pumps for Chrysler products are just as quiet as those from the dealer because NAPA buys them from the same manufacturer Chrysler buys 'em from.

In many cases you have the choice of a complete drop-in assembly or just the pump and motor that has to be installed into the old housing. One way is less expensive but the other way saves time which to mechanics who have to charge by the hour, that also means less money for labor.

They give you enough information in each listing to know if it matches any options on the car. Besides that, it's no different than buying store brand groceries or name brand products. Both fill you up which is the goal. In most cases the higher-priced parts will come with a longer warranty period. That's fine for the part but it won't cover your labor if you have to replace it again. New pumps don't fail very often so I would hunt for the least expensive one I could find. Some mechanics have had bad experiences with certain brands so they only buy name brand parts for their customers' cars. Sometimes manufacturers' parts had a known weak point and aftermarket suppliers design in improvements to take care of that. Their cost of development is lower since they're essentially copying an existing part so they can charge less for it.

There are so many variables and price is just one of them. You asked for "A good one, but not too expensive". Pick one with the best warranty. Very often that is not the most expensive one.