Selling stock with huge capital gains

I have some apple stock from the 90s with a purchase price of 14 ish dollars. It's selling for 300 a share now. I read recently that below certain income levels (96k for married) there are no capital gains? They need to be reported but there is no tax. I was told that I don't want to appear to be washing the stock by selling and then buying the same thing back but if I bought something else, would that be okay? How much stock can I sell if I make 50k a year? Is there a limit?