It shouldn't take too long for the right car to come along. Don’t think its worth changing gearboxes for the “improvement” you might get. If the gearbox is such a worry to you, just buy one with a Mazda box as that is really what you want. Oh, and bear in mind, a very low mileage car doesn’t necessarily mean you have less to worry about...the tyres may be be past their “use-by” date, brake cylinders might be corroded from lack of use...etc
