dell isn't big on publishing their specs, but it seems to be a mid to full tower atx case based on the outside dimensions, so any atx or uatx motherboard should fit. However I offer no guarantee on that (dell stuff is notorious for being upgrade unfriendly) and would just suggest spending the $60 on an antec 300 or similar case.
As for the powersupply i have serious doubts the connectors would have the right pin count for a modern motherboard, and i'm rather sure it lacks sata power connectors. On top of that it's probably getting close to, or is already beyond, the mean time between failure for the model.
long story short, i think it's reached end of life and you should be happy you got your money's worth out of it, and you should just start over, the money saved by attempting to reuse you case and psu are just a small fraction of the total upgrade cost and would be worth it to save headaches.
*edit after taking a long hard look at the service manual for that model, i wouldn't even attempt reusing the case, i've dealt with them before, and in my opinion saving $100 still wouldn't make it worth it