Oh it's a lot different. The original never had a talking protagonist so they added a full story built around the protagonist and he actually speaks in the remake which is fantastic. They added side missions, and all of those boxes and rooms that you can open with the master keys. None of that was in the game. They also redesigned a lot of the levels so that the space station actually makes sense and made the game way bigger in scale. It's really a good remake and worth every penny.
As far as guns go, plasma cutter is king, level that all the way and then level up the force gun for crowd control. All you really need is 2 weapons so you can just focus on the ammo for those. The only other weapon I'd go for is the contact beam but that's 3rd IMO. It pairs well with the force gun so you can use the alt fire on the force gun to create the black hole and suck everything in and then fuck everything up with the alt fire contact beam.