Does anyone know if and how I would be able to switch out the V6 engine for a 4.7L V8?

They put the 4.7L V8 in the 4Runner, which is almost exactly the same as the Tacoma, so I see no reason why it wouldnt work.
Is it really worth all the trouble though? You are looking at only a 20-30 hp difference from the 4.0L V6 to the 4.7L V8. You could put a supercharger on your 4.0L for less money than what it would cost to buy a 4.7L and you would have more performance with a lot less hassle.

If i put the supercharger in how much extra horse power would I recieve as opposed to getting the new engine? Is there any way to have dual superchargers or are they only designed to have one on one engine?

The supercharger brings the 4.0L up to 304 hp, which is about 20 hp more than a 4.7L. Be forewarned though, the TRD supercharger costs $4,500. They definetly dont give those things away!
Ive never seen an engine with dual superchargers, so I dont think that would work.