Better to just RMA, or wait it out? [Mobo/psu]

Ok, so I'm piecing together a build and I first ordered the case/psu and mobo. (I'm a starving student, so I have to widdle away at this). Now before I start, the PSU is or was a junky 500W Apevia that came with the case, and the mobo is a T-series Biostar P43; so get out your squirtguns. Hearing not so great things about the PSU I wanted to make sure it would be alright before I added any more components to the equation and possibly ruin them as well. So, I hooked just the 24pin connector and the fpannel buttons, turned the PSU on, and hit the power button. It worked fine. I said "cool" out loud thinking I made the exception to the crappy-PSU-rule. At least for a little while. I hooked the rest of the fpannel up (sound/usb) and plugging the fans into the PSU and thought I'd give it a nother go just for the hell of it. Turned the PSU back on, hit the power button... WASSAP [spark] from inside the PSU and puff of plasticy smelling poor-craftsmanship smoke came from out of the top fan of the PSU. Now I'm worried a tad as I don't know if my mobo has been affected. I checked the transitors and they all appear to be fine. I cleared the CMOS and hit the reset switch. I found an old (working; tested) Thermaltake 430W psu from an old build and tried to do my stupidity some justice. What happens now is somewhat comforting, but not too reassuring at the same time. With everything hooked up the same exact way, I turn the PSU on and without touching the power button on the case, everything kicks on (except the mobo I assume, as it has no RAM or a Processor). But it only stays on for a short amount of time ~4-5 seconds and turns itself off. The only way I can get it to do it over is if I turn the PSU off and back on again. Now, is there anyway to tell anything about the state of the motherboard from these effects currently? I wont be ordering a processor for another two weeks & only have 26-27 days left on the RMA. RAM, HDD, and a new OCZ PSU are next on my list.

Suggestions, before the weekend is up?