Hi, welcome to the forum! I suggest you post this thread in the Suspension & Brakes section, you'll get a lot more responses. Maybe a mod will move it for you...
I am not familiar with the drum brake set up on a Frontier. On my 200SX, I used a rubber mallet to tap the edges of the drum. Came off easy after a couple of whacks. Oh, and remember to release the parking brake.....I made that mistake...
Also, check to see if the drum has two threaded holes on it. If you can find a bolts to fit those holes, you can pop off the drum by alternately tightening the bolts in the holes.
That's all the advice I can offer, anything else would be specific to the Sentra/200SX platform. I have no idea if they closely resemble the Frontier brake system. Hopefully another member can come along and provide more information....
EDIT - Forgot to mention you should run a search on the forum, maybe someone else has already made a thread about drum brake removal on your vehicle. Good luck.
