I have a Compaq Presario SR1620NX and I had a wavy

I have a Compaq Presario SR1620NX and I had a wavy image on the monitor. I changed to another monitor that I had and it was still wavy. I took the computer to best-buy and they said it was a bad motherboard and gave me an estimate of $775 to repair it. (4 yr old computer out of 3 year warranty)The motherboard is an MSI-7184 Amethystm-GL6E which I have found for as little as $59.
I have an XP disc. Although I have installed RAM memory myself I am generally computer challenged. I wondered how difficult it would be for me to change the motherboard myself. Is it plug and play or at least as easy as adding additional RAM memory ? Ant help or advice would be appreciated. The computer is not that old but I can get much more for the $775 quoted for repair.
Thanks,
Joe Z