The 1100 designation for a Remington shotgun is the model number. Remington makes the 1100 model in a trap version and a field version.
Visit the Remington web site.
400 dollars
Price varies depending on which version, condition.
100-1000 depending on specifics
Best left to a gunsmith
You can request an owner's manual for free at the Remington website.
The Remington Model 1100 shotgun is still in production, hence it would be worth no more than list price - and probably less, if it has been used at all.
100-400 USD
Best to ask a gunsmith for help.
100-8000 USD depending on EXACTLY what you have and its condition.
50-1000 USD or more depending on specifics