Replacing air shocks with gas shocks

Guys i have a cadillac 2006 sts v8 base model, so
the front shocks are leaking, and the rear shocks
are completely gone, and i need to replace them,
but i found out that they are air shocks, and i can't
afford getting new air shocks because they are too
expensive, so i was thinking of replacing them with
gas shocks because they are cheap, it says that
they fit my vehicle, but i need some advices and i
want to know if they would fit or not