At the end of the day you need to ask yourself, what are you looking for? Do you want a quick fix cause you will be selling the car soon, or do you want a fix that will give you peace of mind for the next 200,000km or more?
There is nothing to be confused about bro, it's simple. It's the same as filling up your petrol tank. You spend less if you fill it up halfway, but you get less mileage. Spend a bit more and fill it up full and you'll get more mileage. Just remember there is no guarantee that the engine kosong you get from a chopshop isn't going to smoke after 5,000km.
As for gearbox you can try calling Lionel (012 220 7630) to see if he got cheaper contacts to rebuild for you or not. I've heard a lot of good things about M-Scope and their price is high, but they deliver exceptionally good work. They might not be the best place to go for someone on a budget.
Good luck bro!