Once you remove the gas block/tube, you can remove the assembly as a whole (large strap wrench and start cranking on it...you risk tearing up the tube if you go that route) or, preferably, you can heat gun/hairdryer/etc. the tube back by its proprietary barrel nut which should loosen the epoxy grip enough to get it off the nut, then remove the bbl nut per usual. Reassembly is just as simple and since you are effectively epoxying the tube back onto the barrel nut once you have the barrel/nut reinstalled and properly torqued down, getting the swivel stud back to 6 o'clock is easy as you just eyeball it and make sure its right before allowing the epoxy to set. If you do not want to go the epoxy route upon reinstall, you can carefully drill the CF handguard (I'd go with at least a min of 4 screws...more would be better) and then drill/tap the barrel extension to use set screws to affix the tube that way.
Personally, I'd just scrap the DPMS CF tube and go to one of the Carbon Arms, Carbon Feather LR-308 tubes instead which eliminates the stupid epoxying/semi-permanent install so that you can readily work on your rifle as needed without all the fuss/mess involved with the DPMS tube. The CA tubes use a barrel nut/tube mounting system like other handguards/rail systems out there for the AR platform rifles which is a vastly better design than the DPMS tube.
