Ok SOSH, tell me about club fitting.
This experience has really got me thinking that maybe I could benefit from getting a club fitting and new set of irons. I have never been fitted before so I don't really know what is all involved. Where should I go? I'm assuming that a club fitting goes hand in hand with getting a new set of clubs? Should I go to the fitting with new clubs in hand and they fit them to me or do they tell me which clubs I would benefit from the most and then I make the purchase? Do they do a swing analysis? How much does it cost? What other type of questions should I be ask while I'm there?
Do a simple google search in your area to find a club fitter. (If you're in the Boston area, which it doesn't sound like you are, Joe and Leigh's is the best around). I believe Golf Digest still has a database for best fitters in any state. They can make some adjustments to your current set, but if you're on 15 yo gear, you likely should just get new technology; there's a good portion of marketing involved in year to year new models but that amount of time, you're playing outdated tech.
Do not buy clubs before you get fitted. Go to a shop and browse, see which clubs fit your eye, what falls in your price range, hit them and see what you like, then go to the fitting with maybe 3 or 4 sets in mind. If you find a good fitter, they will have a launch and spin monitor to analyze your results with each and settle on which set is best for you given the stats each club produces.
They will determine if the club head should be bent flat or upright; if the shaft should be lengthened or shortened; what flex your shafts should be; what size grip you should be playing.
This will probably run you about $100-$150 at most places, but they usually give you a credit for that amount if you buy the clubs through them, so it offsets at most places, but that's something you can ask.
Depending on where you go, they will do every club in the bag, driver to lob wedge, or you can just do woods or irons. I would definitely ask them about what wedges you should add to the bag - if your current set of clubs are 15 years old, the lofts on them are likely going to be different than a new set, as current clubs have moved to stronger lofts as a marketing move to make them seem longer hitting. Today's PW is more like a 9 iron ten years ago. You want consistent gaps in your progression, so the SW you have now may be actually the same as a new PW. I would also ask about long irons vs hybrids. That loft change means your current 4I is closer to a new 3I, which might mean you're better off leaving it out and getting a hybrid instead.
It's a fun experience and always exciting to get new sticks. Find a fitter, talk to them when you make the appointment about what you're looking to do and trust the process.
Edit: To expand a little bit on what your experience is going to be, this is what will/should transpire:
You'll show up and they'll have you hit your own clubs to warm up and get some base line readings. You'll discuss sets you've looked at and are interested in and they might have suggestions for you based on what they see from the data and anecdotal evidence you give them, i.e. "I always seem to hook/slice; I can't hit a 4 iron; etc". Depending on the facility, you may be on a range or on a simulator in a studio.
They then will take one of the sets you want to try and usually start out with contact tape on the sole of the club - this will tell them if you need the head to be more flat or upright, based on the contact you're making with the ground. They'll also be able to figure out if you need longer or shorter than stock shafts. They will then attach a device to your shaft to determine flex strength.
They have all these clubs in every configuration (or they have the heads they can change out on the fly) and you'll likely hit the 6 iron for every set you try. You hit maybe 5-8 balls with each and they will whittle it down based on the stats the TrackMan spits out and tell you what they recommend. Then you'll pick out grips, based on feel and size. Then they order the clubs.
Most sets now come 4I-GW (some call it AW; either way it's between your PW and your SW), but companies are pretty flexible these days and with custom fitting, they can play around with that or you can buy clubs individually. If you can rock a 3I, you can add it. If you can't hit a 4I, they can leave it out and you can buy a hybrid instead.
Talk to him about composition of your bag. You ideally want to be able to take a full swing and have roughly 10-15 yards difference moving from one club to another. When I got fitted last at J&L's it was about a 90 minute process and we did a wedge fitting as well, as my wedges were set at lofts to compliment my old set and the new set, the PW was 2 degrees stronger. I may be getting into information overload for you, but when/if you talk to him about wedges, talk to him about bounce as well - if you tend to take a big divot or not makes a difference on what you should be playing.
They also can do putter fittings as well, if that's something you're interested in. For that, they can use your old one and just bend it accordingly, if you're not looking for a new one.