Project #45828: Electrical

I'm requesting help on behalf of my elderly parents. My stepdad is on oxygen and unable to help with upkeep around the house and my Mom, is bedridden. I try to do all that I can for them, as their caregiver, but I can only do so much. So, any help is greatly appreciated.

They have a storm shelter which is under the house, the GFCI which the sump pump plugs into, is crooked and needs to be replaced. As recently as two weeks ago, the GFCI popped and this allowed water to accumulate in the storm shelter, and it rose to the level of the 2nd step. Once I was able to get the water to a level where I could reach the outlet, by the time I push the button to reset it, the top part of the outlet is sticking out and the bottom is pushed back in. If I could get help replacing this, that would be great.

I can purchase the materials if someone will just tell me what all is needed. Thank you for your help.