motor swap

Guys, I need your expert advise...... 2000 firebird 3.8, 5 spd. 205,xxx mi....... head gasket or cracked head. Anyways my ? To you is...... I found this cat selling an engine but from an automatic. Is it a quick bolt on to my car or its more complicated than it semms. Am I better off rebuiding my motor or go ahead and do the swap? Thank you so very much carnales, help me out make a quick descision.