Here is a schematic of a 550-1 -http://www.gunpartscorp.com/Manufacturers/Remington-33454/Rifles-37895/550-1-39530.htm
It should help you get it back together, kinda like building a model kit.
there are a few different ones there.
View Profile: jmgunsmithing - INGunOwners
I bought a 1950's era Remington 513-T Matchmaster for my son's first gun. It had a hair trigger that I thought was dangerous. Jeff took it and made it a nice 3.5 lb trigger.
Highly Recommended. Tell him I sent you.