Good, I think you are about to get into a problem wanting to have a complex solution, I do not say simply because it seems to me, but from my own experience, it is impossible to enumerate the difficulties you will encounter and not to mention the expense of money, but it happened to give you some little encouraging details, the rest depends on your patience and your pocket. The assembly of the mechanical box is the same, that of Golf 3 has to do well, but when the time comes to install the brake and clutch pedals, the gear lever and the control cables, the acceleration control on the engine, the flywheel with the clutch kit and a few more that you will have to make sure you get them in scrap before touching anything of the original. In your place I would try to make an effort and repair it, you will save a lot of headache, I know that in Mexico it is not easy to find a reliable automatic workshop, for now it is best that you think about it with time and calm.