Question about Engine rebuilds?

I have a 1994 Mustang 5.0 stick, with new clutch, brakes oil-pressure sensor, clutch cable rear main seal which I had done last summer, it has 198,000 miles an was thinking on having a engine rebuild since it feels kinda slow, how much will a engine rebuild cost me I'm only 26 years old with only 14,000 which isn't much , some of my friends think a motor rebuild is a waste of a time but the way I look at it why buy a new car when you can just have the engine redone to at lease factory specs.. Is something like this worth doing an is a engine rebuild really expensive ? what consists of a motor rebuild anyways