I WOULD LIKE TO KNOW IF THEY MAKE NIGHT SIGHTS FOR THE KEL TEC P-11 AND WOULD THEY BY HARD TO INSTALL

Yes, they make night sights for a P-11.  

Kel-Tec makes some for $80 installed, just send them your slide.  XS also makes some but they are expensive, look HERE.  (Scroll down until you find them, they are not in order.)

BTW, I have read of plenty of P-11 owners who are happy with the Kel-Tec Night Sights, and the price includes a warranty.  I have seen them for sale on eBay for $40 a few times, but you would have to do the install and get no warranty.

I have never heard of anyone who actually had the XS sights installed.

just a note.

The Tritium inside the Kel-Tec night sights has a limited lifespan of about 5years and replacement is not covered under the warranty.

www.kel-tec.com/p11accessories.html

Do other night sights last longer?

"Top brand" night sights usually carry a warranty of 12 years.  IIRC, the Kel-Tec sights last longer than 5 years, but only carry a warranty for that long.  The XS sights might have a longer warranty, but they cost twice as much.  

For me, the $16/year for night sights is worth it on the P-11.  If they go longer than 5 years it is a bonus.