Ruger doesn't really have a paper warranty to void. If the damage to the pistol is obviously from neglect or misuse, expect to pay for repairs. Ruger will however work on pistols that don't function properly if you call them.
I'm installing my Ghost Rocket today, the Rocket has the TCT (Trigger Control Tab), it keeps the overtravel down and is NOT a direct drop-in part and requires multiple teardowns to get it's fit/function correct. The Ultimate is a drop-in part and accomplishes the same weight drop as the Rocket but has no TCT to stop overtravel. The other (Tactical?) is a less severe drop in weight to 5.5 rather the other model's advertised 3.5 weight. It does have the TCT and requires the same fitting as the Rocket would need.
If your SR9 is 100% reliable and you get any of the Ghost Trigger Connectors and something goes wrong after installation. Meaning, Light Strikes, Failure to Reset or some other function related problem (NOT Failure to Eject, shouldn't be related to the Trigger) call Ghost about the problem and see about a new part or troubleshooting it over the phone. They will likely replace the part at no charge to you (except maybe shipping). Ghost's Customer Service is excellent for as small a company as they really are.
If your unsure about the cause of the problem, reinstall the Stock Trigger Connector and see if the problem changes or goes away. If it goes away, reinstall the Ghost trigger to confirm you've isolated the problem. Then call Ghost. If the problem stays, leave the stock connector in place and call Ruger. Do not send them a SR9/c with a Ghost connector as they might replace it with a stock part and charge you parts/labor for the installation. Better safe than sorry.
Note that if there is a problem with the internals and parts are replaced, the drop-in Ultimate will still go back in. The Rocket or Tactical model with TCT may need to be re-fit or even replaced depending on variances in the parts from your stock configuration before the repair.
If your handy and wouldn't mind the extra work for a better overtravel, get the Rocket, if your looking for a simple one stop solution, get the Ultimate.
Also, it's important to note that the advertised weights DO NOT transfer directly to the new pull of
your gun. Variances in the SR9 triggers are astoundingly different and no gun will react the same. It will get lighter and should be better, but don't expect the 3.5 or 5.5 advertised pulls. Ghost notes this on the Glock parts that to achieve a 3.5 pound pull you will need new lighter springs to compliment the new connector. There are no such spring sets for the SR9/c as of yet.
Hope this helps
Josh