I just lost my starting shortstop to the 60-day DL. I'm currently in very good shape to make the playoffs (we will see how this injury affects things). Our league has passed the transaction deadline (there's about 30 games left in the season). I just want to make sure my only options are to roll with the players I've currently got on my big league squad, or to possibly promote somebody on my 40-man roster up to the ML team (he will be eligible for the playoffs correct?). However if I trade for somebody or sign a free agent, he won't be eligible for my playoff roster?

Whoever is on your 40-man the moment roster expansion is allowed is eligible for your playoff roster. This includes a player you acquire in trade (and assign) before roster expansion.

Roster expansion occurs with 25 games left in the season-- so you'll have to make that trade before 11 PM tonight (and then assign the player before 3 AM Sunday morning, since it takes 24 hours to clear a trade) in order to get a player playoff-eligible.

dedelman is on it. Anyone on your 40-man roster is eligible for the playoffs, regardless if they are in the majors or minors -- including acquisitions (make sure to assign player).

Thanks for the info!