98 Cadillac Deville

I bought this car at a great deal cause, supposely, it needed an oil pump... I test drove it, drives great. So I bought it, it's about an hour drive from where I live. I took the oil cap off, gave it gas and it got on my hand, this means the oil pump is good right? So I'm driving down the road, car is saying turn off and chimes won't shut off...I'm like hell, I'll risk driving it like this. I drove it like that for an hour, no engine noise or knocking, drove perfect besides them annoying chimes. It did not over-heat, the car never gave me problems nor did it make any weird noises. This leads me to the oil sending unit. So I've never been a chevy/caddilac man. I'm no mechanic.. But I do my oil changes, rotors, brakes, plugs, stuff of that nature. Do you think I could change the oil sending unit? One more thing, where is the oil sending unit located on this car?

Thanks guys.