Should I strictly invest in the S&P 500 for retirement

I am 28 and I just sold my home I purchased in 2020. I’m sitting on a nice chunk of change and I want to get rid of it…strategically. I’ve been working with SWPPX (Charles Schwab index fund S&P 500) and I already have about 25k in there. Also, should I pay off my car? It’s 28k and my interest rate is 6.2%. $S&P 500 Index(.SPX.US)$ $Nasdaq Composite Index(.IXIC.US)$