At least in PT4 you can check the sample size for the stat by just hovering the mouse over it. Overall hands isn't goodish indicator cos someone with same hand numbers might have a lot less sample size in that one stat.
Won@showdown for an example depends greatly on player's VPIP and postflop fishiness. Someone with 1K hands might have gone to showdown 200 times and someone else with 1K hands might have gone only 15. So always check the actual sample size.
No one can tell where the borderline for "reliable" sample size is. If someone has folded to steal 66% it's a bit different if it's 2/3, 45/68 or 244/366. That's where you have to estimate the probabilities. Stats don't give you straight answers, they just give you information. But poker is a game of imperfect information, so you have to use your poker skills to use that information.
If someone wins at showdown 25% (2/8), the stat just tells you that the opponent has won twice out of 8 possibilities. It doesn't tell you pot sizes, number of players in the showdown or the actual situations (bad calls/bluffs or setups). It tells you that it is probable that the opponent goes to showdowns with wider range. When the sample size goes up and the percentage stays low, it tells you that it is more and more probable.