Your question answers itself.
About 275 in good condition
1930-1947
75-400 USD
Tough question, the Remington model 550 is a .22 rifle not a 12 gauge shotgun.
* about Y8.50. if your throw some ammo you may be able to fetch up to Y10.00 (yen)
Take it to a gunsmith
Take it to a professional
50-200 or so
This model Cross refernces out to a Remington Sportsman 58, introduced in 1956, the Sportsman-58 was Remington's first gas-operated shotgun. You can request an owners manual for obsolete firearms at www.remington.com click on sportsmans library, then downloads, then owners manuals, then click obsolete owners manuals, you will have to register but it is worth it to get the free manual.
30p
800