need help!!!

ok so i am new to the mazda trucks and i got a 1984 mazda b2000 and i am in the process of putting new speakers in my truck, when i found out that there is a 4 inch speaker that can go in the dash. and for some reason this is kicking my butt on how to put that speaker in there. so can can someone tell how to do this. and if i have to take the dash off, how do i do that.
-thanks

Don't know about those early B2000 models, but on the 1986-1993 B2000-B2200-B2600 models there's a speaker grille and swapping speakers is a 10 minute job - at most.