Engine Swap

[buraot]

I am planning to upgrade my Elantra 91 engine..I think it has a DOHC 16-valve engine(correct me if I'm wrong)..

What could be the closest engine swap I could make?(Of course, with improvements on speed, driveability, etc) In such a way that most of the major parts are not to be replaced..(Do I need to replace my ECU as well?)

How much would it cost me?

Note:

I would also like to convert it from manual to power steering...(what power steering assembly should I look for? Some say a PS assembly from Mitsu Lancer could be used.)