Lots of variables here.
1. Yes, there are lots of private companies that do service on all FB series. Not sure your local area but definitely ask around - ask your major vendors, ask your material suppliers, ask your ink suppliers - these people know people, or are people!
2. Yes, it looks like you have several heads out. DO NOT BUY PRINT HEADS ONLINE FOR A DISCOUNT PRICE! YOU WILL BE SCAMMED! You've been warned!
3. Changing the heads IS "easy", but of course anything is easy once you know how to do it! If it's worth a day of your time to learn how to install and then align the heads, then you can do it if you're mechanically inclined. If it's not worth your time or not your inclination, then definitely pay a local professional to do it.
As far as pricing goes? I'd say you have at least 9 heads out. Common dealer pricing on those Gen III (from memory) heads is like $2000 per.
Try as you might, there's NO way around that cost. You need $18k worth of heads, that's a fact.
Next, you need to know WHY you need all of those heads replaced. In my experience, that's damage. Those heads aren't a beautiful design, but they sure are durable. You can hit them, fill them with air, rub them with chemicals, head strike them, etc. Something happened or is a practice that is hurting them and you definitely need to know what that is before moving forward. I have worked on tons of those printers and I have never seen head failures like that which suddenly caused a print quality issue.