Is this for your 05? Most guys keep the factory ECU, and just have it tuned, rather than running a standalone. The cost really depends how much boost you want to run. The more boost you want, the higher the cost will get, because you'll have to modify more and more.
I'd budget $2000 MINIMUM for any type of forced induction setup. You might be able to find a used Whipple supercharger kit for the 3.0 for a little under $2000, but the supporting mods and tune will add to your cost. Turbo setups are completely custom, so you'd better know your way around a welder, or get ready to pay big bucks for a shop to do it for you.
For 10lbs, you'd need larger injectors a larger MAF, and a good tune, on top of the cost of your power adder.( $2000-$2500ish)
If you want to run 15 lbs, you'll need a new fuel pump in addition to the other things I've mentioned. ($2500-$3500)
+20lbs would probably need forged internals, and custom ARP fasteners in the bottom end, copper head gaskets, a balance job, etc (no one does this because it's crazy expensive).
For any of these setups, you'd want a wideband setup, some gauges to keep an eye on things, and fresh 02's.
For reference, I'm currently building a flex fuel, highly modifed 3.0 with a whipple supercharger, balanced bottom end, roller rockers, ceramic coated headers, arp head studs, stiffer springs, tons of porting/polishing, and 42lb injectors. Hoping for somewhere in the neighborhood of 12-14lbs of boost. At this point, I've got about 5 grand in parts, and that's with me doing all of the port/polish work myself.
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