Before I went through all that, I'd try doing the CSFI to MPFI Spider Conversion first. Combined with a tune or programmer and some airflow upgrade (cold air intake kit, headers, exhaust) you can get some pretty impressive results.
Rock Auto and Amazon both sell the new spider and this is actually a GM recommended upgrade. If you were to go to the dealer because your CSFI spider crapped out (as they're known to do) they're supposed to do this upgrade.
Here's an overview.
http://www.fuelinjector.citymaker.com/Vortec_spider_fuel_injection_conversion.html
I have done this upgrade on my truck and I'm extremely pleased with it. The power, throttle response, smoothness, and fuel economy are better than they have ever been. Of course I have it combined with other upgrades to improve airflow and performance. See my signature.
FYI, I did this conversion myself, and it was not an entry level task. It's doable at home, but for those reading, it's not a first timer or beginner job. You have to take most of the top of the engine apart or off. Be SURE you photograph and document where you got everything from or you be screwed. Trust me on that one. If you look up videos on this on YouTube, some of them remove the distributor. Totally not necessary and a total PITA on these trucks since you can't re-time the distributor without a scan tool. You should however remove the serpentine belt and unbolt the A/C compressor if you have one and flip the whole assembly over onto the fender well where the air cleaner box goes. This way you don't have to de-pressurize it or deal with the "freon" etc.
Good luck.