I have recently acquired a 1998 5 speed manual transmission v6 mustang
and I am wondering if I can put a turbo in it
Yup, you sure can. Search for a kit online. I will tell you that it will cost thousands of dollars to buy an install. In my opinion, it is not worth the $$ you will spend.
A supercharger might be better and easier but buying a V8 Stang is the smart move.