1. Establish a defense
As usual, Marines and some bunkers will do the job here.
2. Build a ground force
More Marines, Medics, a few Firebats, and possibly a few Marauders, especially if you've upgraded them with the ammo that slows enemies.
3. Begin rescuing drop pods, be picky
Since you've already got decent infantry, try and focus on rescuing the aerial units and heavy weapons so you won't have to waste resources building the required structures
4. Push towards Warfield's downed ship with mercenary air units
Since your forces are somewhat limited here, take full advantage of the mercenary units, especially the mercenary Battlecruiser. If you opt to use the Battlecruiser you should be able to loop around behind the Nydus Worms and with the help of some Banshees take out the Spore Colonies.
5. Destroy the Nydus Worms
With the Spore Colonies down you'll be able to individually take down each worm with the Battlecruiser's lasers and Yamato Gun. If you park the ship over Gen Warfield's bunkers his SCVs will actually repair the Battlecruiser for you. If you start taking too much damage, just pull back to your area to the north and none of the ground units will be able to hit you.