gmc 4.3l engine problem (broken rod?)?

[jim s]

i have a 97 gmc sonoma w/ the 4.3l vortec. the engine overheated and when i pulled over it shuddered to a halt i towed it home and it started the next day but it had a really loud banging sound and shuddered badly. i haven't cranked it since because i thought i might destroy the block by doing so. my bud told me it might be a broken lifter or rocker. what are the chances i have to replace the engine vs. minor upper engine repair? i havent done a compression check yet cause i work 80 hrs a week. what would a compression check show anyway? thanks!