You can have them tested for lie to see if they are too upright or flat. They won't adjust cast clubs typically because they will likely break, but you can still have them tested. I used to have this done at Dick's SG, but I don't know if they still do it since they got rid of all their pros.
If they work well for you then you probably don't need to pick up some new clubs unless you really want to. I would say analyze your game and see where your weaknesses are then see if new clubs would help that issue. For instance having large gaps between clubs or having a consistent miss like always going right/left or thin/heavy.
So last night, I dreamed that I was going to play golf. It was back in Ohio (I think), but it occurred to me that I have played this course in my dreams before. It is a course I have never played IRL...
I was in your spot a few years ago and started with a RAM setup as I didn't know if I would like golf. Cost me $200 for the whole 9 yards. Ended up loving golf and now I have tons of clubs.
$300 is not a ton of money for a whole setup if you want to stay away from something similar to what you currently have. Other posters have put up good ideas for you to follow. Being a Lefty is what will limit you the most. If you are not sure if your lengths, lies and grip sizes are correct Ping has a great system to help you find what does fit you and you can always use the info for other clubs. From a Ping fitting I know that I want 1" longer clubs and 1 degree upright. Now when I browse on the Bay I look for stick that fit those two details. Makes used shopping a lot easier.
There are plenty of good deals out there. Be patient and keep looking. Online, used stores and word of mouth. Good luck to you and I hope you get a nice setup that works for you.
I saw the same thing when I did my little bit of internet research yesterday, it looks like the PGA apprentice training is aimed at those who will end up working at a golf club. I know from my club that the job of the PGA staff includes managing day-to-day golf operations, running the retail pro-shop business, running club tournaments, marketing and running outside golf events, as well as a bit of instruction. @iacas, do you know what percentage of PGA (or other) golf professionals are in this type of situation, as opposed to those who concentrate almost entirely on instruction as you do?
Another update from Florida, Paul's 70 put him in a 5-way tie for second, two behind the leader. Unless he breaks a leg, he seems likely to make the cut at the end of today and move on to the weekend. I wish the PGA had real-time scoring, so I could watch through the day!