To remove the plug on a Remington 870 series all you need to do is unscrew the cap on the end of the magazine tube. Carefully because it holds in the magazine spring. the plug is the rod that is inserted in the spring so it cannot compress fully to limit capacity so just take it out and screw the cap back on (the cap compresses the spring) and voila. takes about twenty seconds.
Remove the cap from the end of the tube and be careful of the spring which is under pressure. The plug will come out with the cap.
Yes.
The average price of a Remington 870 Express Magnum pump 12 gauge shotgun "brand new" is about 300-450 dollars. I got mine used for $250
They are about 6" long.
The Express version of the 870 Remington is normally either 12 or 20 gauge. Gauge desigantion is marked on the barrels left, rear end.
Depends on what it is choked.
About $325-$350
the express is the cheaper model Remington came out with. There are many more models like the tactical ones and the wingmaster. The wingmaster is one of the better quality models.
The 870 Wingmaster is still made in .410
100-375 USD
Around $350 depending condition.
There are many places one might go to find a review for the Remington 870 Express. The most reputable resource one has is the Consumer Reports website.