I was going to (read I did, then freaked out) do something similar.
The computer I did it to is as follows:
Aopen MB (can't recall model, & I'm not at home)
Maxtor 40 gig (I think its a 640x or something)
Creative 52x carom
Celeron 1.0a
Zalman flower cooler
compusa no name 250Wpsu
anyhow, I noticed that the metal casing on the psu was never all that warm, most times it was cool to the touch. (ambient of house between 23 - 27C depending on where and when) I decided to see if it really needed the fan. So I took the fan out. let it sit for about 10 min and thought, hmm, maybe I should be measuring the temps instead of just watching it. I had my wife drive out to the store and pick up a thermometer. (I being in no condition to drive. Which is probably why I attempted said project without one in the first place. Hind sight is 20/20 or in my case 15/35
) In any event, played with the probe in numerous positions letting the computer do what it normally does and serve me files and occ. browse the web. It never got above 43C in any spot. I let it run over night having set the alarm to go off it hit 48C. (When I woke up I think it was down around 30C, it's been awhile) Being sober at this time (that morning) I decided I should do it all again stressing the system.
I turned it off as soon as it hit 50. It did take a while though. And none of the other components really seamed too much warmer.
I hooked a fan (vantec stealth) to a 5v line and then ran the stress tests again. never got higher then 40C. and usually is nowhere near it. It's usually about 2 - 3 degrees over room temperature. but then again it usually just stores files and occasionally surfs the web. I have the fan set to go on when the temp on the Mosfet hits 40 and it seems to shut off when it hits 35.
The other components even without the fan didn't seem all that much warmer, but I think with any more wattage, or prolonged exposure they would definitely be a concern.
Personally a leak in the PSU doesn't sound good to me. No leaks sound good, but that one sounds really bad, and it would be a PIA to check for leaks.