Gear Box

I have a 92 SVX Auto - I live in Australia - and it has developed a problem where the engine tends to overrev without a proportionate increase in forward movement as if the automatic gears are jumping from first to top without using the 2nd gear. I am not mechanically minded, but presume this is a 3 speed automatic gear box and wonder what the problem is and would appreciate any comments which would tell me how to correct the cause of the problem and what the necessary rectification is, and whether it would be an expensive procedure to correct it. The vehicle has done approximately 90K miles (145k kms).
Another problem is that there is a tapping which appears to come from the engine, and this also developed recently.
I have no idea as to the expected lifespan of these vehicles, and the engine in this particular vehicle is a 3Lt none turbo.
I look forward to any comments, especially as this is my first post.