Yes, but with caution. Remember that you are not connecting to the circuit breakers (which are AC) so more than likely there is no BUS to help you out.
You are connecting to the fuses which typically are powered by a single, heavier gauge wire into the back of the fuse panel.
From the fuse panel you will then have a bunch of smaller fused wires out to the various 12v applications. You should be able to isolate a single 12v wire (I've used overhead lights in my trailer) and tap into that wire for your 12v positive. By going this route you probably do not need a fuse as the wire you tapped into is already fused at the panel.
As far as the negative, you might get lucky and the fuse panel also has a connected ground wire. If no ground wire then you can run a separate ground wire to somewhere. This is where a multimeter to check continuity comes in really handy. It might be possible to tap into the ground BUS on the AC side of the breaker panel. But this is typically advised against. You really want to find a ground location that is a bit isolated from the AC side of the system.
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2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup