My family has neglected our turtle for years, help

It makes me extremely sad to talk about this, my turtle has been in my family longer than I have. My turtle is about 23 years old and for the past recent years it's been in awful shape and very neglected. We leave the turtle in a corner and sometimes forget to feed it, but its still alive. I am very ashamed and I realized how much that turtle has been part of my life. I saw baby turtles the other day in the street and now I want to change how my turtle has been living, so i have a few questions.

are there vets that will see turtles or is that stupid? I know there is vets for like cats, dogs and birds but never have I seen a turtle at a vet. My turtle's water become extremely dirty in a matter of hours after bathing it, is there anything i can do about that? Should I get my turtle a heating light? Never have we used it before and my turtle continues to live, is it necessary at this point?

thanks! and also are there any tips that I can do take care of it?

It is never too late to make things better for the turtle.

A Red-ear slider of that size should have a tank with at least 100 gallons of water to play in, heated to 75-80 degrees, filtered aggressively, several basking sites to choose from heated to about 90, and lighting that simulates the sun- including ultra-violet rays.

It takes some work and money to set this all up, but there are ways to simplify it. For example, a kiddie pool, plastic stock tank, or indoor pond liner can be used for the tank instead of a giant (and expensive) aquarium.