Shoebox 4500 in need of assistance

1. I don't think any company services them anymore. You might be able to find some individual willing/able to do it, but the weight of the Shoebox is going to make that not very feasible to ship to them.
2. here, possibly https://ocolabs.com/product-category/spare-parts/
3. There are some youtube videos still available from when Tom had the Shoebox company running.

I just turned over 90 hours on my F10 last week. Haven't needed to replace an oring yet. It's still pumping at the same rate it always has (87CF scba tank goes up 100psi for every 10 minutes that it runs) and I'm crossing my fingers that it just keeps cranking away.