Pretty small map for TNT’s standards, though if you go for secrets, the excessive amount of backtracking in the central area makes this a decent length.
You’ll want to take your time in the big indoor arena to avoid alerting everyone at once, namely kill the Pinky mob first before you open the switch to release the Pain Elemental. You want as few enemies around as possible lest you be swarmed with tons of Lost Souls.
The secret room with the Super Shotgun and Barons is the trickiest part of the map, but there’s a trick here in your favor. Open the walls so you can use the one way teleporters and telefrag the barons. There’s one you’ll have to kill the hard way, but with the Super Shotgun that won’t be too hard.