I have a Lexus Es300 (1990) although it is in good condition but seems to have some problems in engine. It takes two tries to start it and gives abnormal noise to start. I want to replace it's engine. Please tell me, can i do so my self, moreover how much it will cost to me if i get it repaired in workshop? Thanks in advance.

Based on what you describe, the problem could be the starter or flywheel rather than the engine.

Right. It sounds like the flywheel may be missing some 'teeth'.. Worn out..