1998 Nissan Frontier AC issue

[gid]

I have a 98 Nissan Frontier 4x4 king cab\extended cab that has an ac issue. When I am driving around it always starts off blowing cold air. After about 10 minutes is starts blowing hot. After another 5 minutes it will start blowing cold again. It does this off and on the entire time. I find that when I am stopped it blows hot much quicker. Do y'all know what that might be?

[Ruff09]

My brothers 2003 does same thing and his compressor is shot (he took it to shop and it had low pressure). I was looking on forum to see if anybody knows the steps to replace his compressor. His is a 4 cylinder.