Welcome!
Once you get specific questions regarding the wiring aspects of your swap, just ask away in the LS1 conversions section of the forum. You'll receive plenty of help. To help make your swap go easier, get schematics for both your 5.3 donor vehicle and your swap project vehicle. (Astro) The wiring isn't as bad as you might of heard and depending on your conversion harness choice (Allen, Speartech, Painless, or convert it yourself) it can be as simple as a 4 or 5 wire connect.