It would be in best interest to rebuild the engine if its complete - its a very simple engine to work on, you would need to buy some special sockets though - all for about Rs 1000/- a small set of E-Torx and a couple of male torx
The rest are standard metric tools. You can also rebuild its transmission completely with new parts and have a very reliable piece
As for replacing engines with japanese - dont do it - The original ZF transmissions in BMWs are tiny compared to any standard issue japanese RWD transmission, you would need to broach the tunnel (structural strength compromised here) to make the transmission fit.
The small problematic parts can be got from sources in mid east or even UK - as they can be shipped easily with someone. The idle control valve, distributor cap/wires, AFM, ECU, main crank pulley etc. Buy a repair manual for this car and rework everything to originality - you will love the car, if you infect it with a toyota engine/parts - you'll wish you hadnt bought it.
