Van will not crank

Was this a problem before you started the work you have out lined? If not re-check your work as you may have knocked loose a sensor wire on not connected something securely, post back with your findings for further assistance.

Fuel pumps are a very common problem on Chevy S10s, Blazers, and Astros. Every mile after about 150,000 is a blessing. I'd start by checking that. An easy way to check is to spray some starting fluid into the intake and see if it starts and runs for a second or two. If it starts and then dies, or even idles, then it's most likely a fuel delivery issue (the pump or a very clogged fuel filter).

If it started and died, then I'd say to borrow a fuel pressure tester from AutoZone or whatever auto parts store (should be free to borrow) has one and check it. It should build up to and maintain close to 60 psi for a while. Here's a general how-to guide: https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let us know what you find.