Lifters?

I'm not completely familiar with the grand am's engine, its my dads car. Its a 93 grand am. The engine is shaking pretty bad and there is a pretty loud ticking noise. The engine has around 14k on it (new one w/7k was swapped in) The mechanic we took it to said it was the lifters. Does that sound like a possibility? And what do the lifters do? Finally If anyone can tell me what the price i'm looking at? Any help would be great, thx.

what size motor are we talking about?

Honestly i don't know, Its a 6 cylinder. It says 3300 on the motor.