Like many others have mentioned, I buy most of my clubs from Ebay as well. I've never had any problems with them, although I only buy clubs from reputable sellers (with at least 1000 transactions). This is a pretty useful site that tracks Ebay seller feedback: http://www.toolhaus.org/ I also google these sellers online, and often times you can find golf forums talking about if a seller if legit or not.
In terms of the club fitting, there are a lot of places that can fit clubs once you buy from Ebay. However, I would
ONLY
go to a reputable fitter. I've had my MP-52 for about 2 years now, and I tried 4 different fitters. First time was from Golfsmith, and the sales person obviously had no idea what he was doing. I paid $20 dollars just to hit on the lie board, with no measurement or launch monitor stats (since I'm a lefty and the monitor was set up for righties). The next 2 times were at local golf courses, and both fitters claimed that they were professional fitters. Both times were with lie board only at outdoor ranges, and both concluded that the clubs fit me perfectly! Each of them ended up trying to sell me golf lessons instead. Since I was never comfortable with the fitting sessions, I never got my clubs fitted, until recently...
2 weeks ago I went to a famous club fitter located in South San Francisco area (I think some of you should know who he is). He does his work in his garage, which kind of worried me in the beginning. After warming up, he got me on the launch monitor. Instead of letting me hit right away, he spent the next 10 minutes adjusting the launch monitor to ensure that the readings were correct. He then measured my height, arm length, wrist to ground distance, and the whole nine yards. I didn't start hitting until 30minutes into it. He also asked me to hit at least 20 to 30 shots with the lie board so that he can get a good range of data. He changed the impact tape after every 3 shots, which really impressed me. Immediately he noticed that the clubs were too upright for me, which caused me to pull my shots. He bent my 6iron right on the spot for 2* flatter, and OMG the pull shots were gone. My shots became so much more consistent and I also noticed a 5 - 10yd gain per hit. He also suggested that I am hitting my shots too high due to the Project X shaft; however, instead of trying to sell me some Dynamic Gold S300, he just told me to move the ball farther back in my stance to lower the ball flight.
During the fitting, he also noticed a few flaws in my swing. He gave me great tips right away instead of trying to sell me lessons, which helped me improving my golf swing tremendously. The whole session took about 2hrs, and he adjusted all of my irons right away. I was so impressed with the experience that I went back on Thursday to get my driver and 3 wood fitted. I did spend a pretty penny on the new shafts but i can't wait to get them back in 2 weeks!!!
So what I am trying to say is that yes, you can definitely fit your clubs even if you purchase from Ebay. Cast irons can be adjusted as well, but probably within 2* by a good fitter. If you have a pretty consistent swing then I would definitely go get my clubs fitted. It's the best golf investment I've ever spent! I am no longer a club ho...