You might want to take a trip over to rugerforum.com and read the endless posts on the P-345. I bought one (KP-345PR) when they first came out (3-digit S/N). The gun has rated well with the gun rags and got the "Gun of the year" award. No doubt, Ruger's design is excellent. It's sturdy, accurate, and packs well.
Function is a different story. Though many owners report flawless function, others have had major problems related to quality control of the internal parts. My gun had 13 documented problems. The newer guns seem to be better as Ruger has improved their manufacturing processes.
If I had it to do over again, I would NOT buy the P-345. In fact I got so frustrated with my gun that I bought a SIG P-220. Same basic profile but the SIG works perfect in all respects (cost about double of the P-345).
My P-345 had all the problems repaired and is now shooting fine. This gun is available with a blue or stainless slide and with or without the Picatinney Rail. It comes with a standard safety or a decocker only. Mine has the rail and standard safety. Had I waited a bit longer, I would have bought the non-rail model with the decocker only that are more "holster friendly". The gun has the new safety feature including a key lock, loaded chamber indicator, and magazine disconnect.
Odds are you will get a good one and be very happy with it. Then again, you may get one like mine.