At this point, I would say that you would probably wouldn't have to worry too much. If something major was going to break, it would have done it by now. Also, any dealer can use the VIN to check if proper updates were done... I would recommend doing this.
Being the first model year, the '03 Firecats had their share of problems, particularly the F7. I do, however, think they get a "bad rap" sometimes. Most of the early blown engines were caused by bad setup procedures, (air trapped in cooling system) and lots of the smaller items have been updated or corrected in some way. The '03 F7 has been a great sled for many, and I don't think it's an automatic lemon by any means. Besides, the '03s are still the fastest 700s out there.
If the updates have been done, and the sled was otherwise cared for in a decent manner, I wouldn't worry about buying an '03 F7.
I bought mine new and in 4500 miles have had 2 top ends(piston problems), 1 pipe, the recoil fell off, lost count on how many idlers have fallen off, idlers fallen off wrecked the track, 2 ropes, 2 limiter straps, 1 gas guage and 1 snow flap an about 5 belts and other then that it has been ok... fastest sled out there
standard suspension is a joke, 1.375 track is the only track that does the sled justice, get rid of the coupler blocks, run at least 6 inches of carbide in the front and enjoy,,,
tip on recoil-loc-tite bolts, rear sno flap needs to be tied up, they make better rope for the recoil-spectra i think it is called, keep close eye on idlers and run new bearing in them every year, keep a close eye on the belt and when it starts to frey=replace...
cat is still replacing pipes under warranty if you have good dealer.
the power of these things is unreal, the handling is unique but in a good way, especially in a ditch. the top speed is Awsome. there is no other sled out there like it before or ever again... get one
you will really like the batteryless efi, it is hard on gas, about 100 miles to a tank but she will start on 2nd-3rd pull every time and whe warm 1/2 pull. no choke is Nice