I've only had my car for less than a year (in which time, I've done just over 6,000 miles): but, as long as the gearbox is looked after (i.e. replacing the filter and the oil at the recommended service intervals), in my experience, it's reliable, and smooth as silk...!
I get just over 40 mpg in mine (driving it permanently as an auto; and usually with the E button on -- which limits the revs to about 4,300...), on average (on a mix of town and countryside roads...) -- but this can go up to over 50, cruising on the motorway; but is never less than the very high thirties. It's also obviously a bit more economical in warmer temperatures; and I find (presuming it's the 16v engine) that it runs better and more efficiently (i.e. less pennies per mile) on super unleaded (i.e. Shell V-Power).
As to the price, I paid a little bit less than that for a 70-odd-thousand-miles 2002 car. If it has a FSH, and not too many owners, seems a good price to me... -- but have a look around the Punto Mk2/b section of the Forum for points to look out for....
PS: Sorry, I forgot my manners... -- Welcome to the Forum...!