That is true, but it's very hard to find this model in good condition. You might get a car with good engine but the suspension might not be upto the mark, point is to find a perfectly good vehicle will probably take a lot of time. No matter how good a car is when you are going for such old models, it's routine to spend some money to bring it up to the mark. If your car is in perfect condition i'd rather go for the swap. Unless ofcourse you are concerned with resale. Even so the resale on a 6 lac car is not that big of an issue.
It'll be better to swap the whole engine rather than just the gear. If you want to just change the transmission keep in mind that for quality work it'll be expensive. Above 30k at the very least.