Ok, i have this 83 datsun 280zx non-turbo. I'm burning oil and a lot is going
to the spark plugs. I'm not trying to get burn, but one mechanic said that a seal needs to be replace inside the engine and it's best to just rebuilt the engine.
Does anyone have a better suggestions? I'm burning oil and every week i have to add one quart of oil and the oil is coming out to the spark plugs. Do you know how much should i pay to rebuild my engine?

 

There are many seals, and rings, and other things that can wear down and consume oil. For a mechanic to pull the motor, rebuild it, and drop it back in... you're looking at $2k to $4k. If you pull the motor yourself, tear it down, and take it to a machine shop to have them check it and rebuild it... you're looking at $500 to $1k.

But, let's start at Automotive Repair Basics 101...

#1: Download the FSM for free from XenonS130 - S130 Reference
#2: Check the compression on all 6 cylinders.