I have an old sears guitar model number 319.12120000 ... pretty much the same as this one ...

*link removed*

but I need to get some new tuners and tuning posts for it...

my question is, can I use any tuning posts and tuners for this gutiar?
if I can't

how do I figure out which ones I need?

thanks in advance...

remove ebay link or get warned.

i've got 33 days left of a warning because of the exact same reason you just posted one.
Belief is a beautiful armour but makes for the heaviest sword.
Tuning machines are pretty easily replaced or upgraded; you just need to get the right size.

Ideally, the shaft size and length must be the same, and the screw holes should line up so that you don't have to drill new holes.
Stew-Mac: http://www.stewmac.com/shop/Tuners.html

has just about anything you could want and handy reference guides to make sure you get the right size.