49er hull weight

I may be wrong, but don't 9ers tend to ge a bit floppy and have issues with the wing mounts on older models. Not sure about weight, they are heavy boats anyway.  But i would doubt it would make much difference as a training boat. Even if it had taken on a bit.

It really depends on the boat. My old 49er GBR055 although old was in pristine condition. The boat had had two previous owners before me the first of which had it as an Olympic campaign boat, and even etended his garage so that the mast fitted inside! The second owners were the class chairman in the uk and the class website guy. They spent almost as much as a new boat on getting everything sorted out by Ovi's to the point where it was effectively re-built to the same spec. as boats in the 700 numbers.
Just look over it really carefully and check its not loosing rig tension. Wing attachment slides need to be checked, as if they rip out in a capsize they make a mess.