First off, the worst thing he could have done is buy that wimpy v6. underpowered junker. If you want an easy swap with enough power and lots of torque, Put in the I6 that was an option. That and the tranny should be an easy swap in. Its got enough power and lots of really low end torque. If thats not enough power, there are supercharger kits for it. As if the low end torque wasn't already sufficient.
As for v8 swaps, they have been done, and not that bad to do i've heard. The engine bay fits that i6, accessories and radiator all in there with about an inch to spare. That i6 is pretty long, so fitting a v-anything in there shouldn't really be an issue.
Picture kinda blows it outta proportion, but thats a long engine. And it goes all the way to the firewall basically. Tranny is mounted much further back than i woulda expected. v-8 shouldn't be a problem to fit.