halocline
Contributor
It seems to be an old SP-5, not an FDX10. The second stage is an original Delta, not a Delta 4.
If it's a MK5 with 5 LP ports (one on the end) and 2 HP ports, it would really be almost impossible to get a better all around 1st stage. Unless there's something wrong with it, there's no reason whatsoever to get a MK20. For the 2nd stage, I don't really know anything about your oceanic, but certainly you could find a 109, balanced/adjustable, or G250 at a reasonable price and you'd have a great reg set.
I know that lone star scuba is a scubapro dealer. The've been around a long time, nice folks. I don't know who's servicing their regs for them, but if you have any trouble finding someone to work on it, send me a PM and I'll try to help you. There's a SB member named couv who has restored and sold several of the 109 metal 2nd stages. I'd contact him; he's a great guy, knows a lot about the regs, and is very honest and trustworthy to buy from.