Recommend you let a gunsmith do it.
The trigger is held by 2 screws and one pin that needs to be pressed out. See the link at the bottom of this page.
No. Trigger guards for these were made of plastic.
There is a website www.rediscovered-shooting-treasures.com/mossberg that offers copies of the original factory instruction sheet for the 810 models. This is the "manual" that came with your rifle and covers a lot of information including trigger adjustment.
I believe this rifle was made by Mossberg and is the Mossberg 46B. Do a search for photos of the 46B Mossberg to see if it is a match. If so, try Havlin Sales & Service as they may have a replacement trigger guard.
Do not attempt to use other than a Mossberg bolt made for that rifle.
Mossberg made the model 207.Big difference between Marlin mdel (205) rifle is Marlin has pistolgrip+ Mossberg doesn't. Mossberg's trigger also pinned to lever .
Cannot find an exact match- but if your trigger guard is black plastic- and especially if it has finger grooves in the tail of the guard- it was probably made by Mossberg. You can order replacement trigger guards from havlinsales.com There are 3 different trigger guards- check the photos to see if they match your rifle.
A Mossberg 22 rifle such as the Plinkster depending on the condition is worth around $150-200.
open the bolt all the way back and pull trigger and bolt will pull out do the same to put it back in
With the exception of taking the action out of the stock, and the bolt out of the action- it is not necessary to disassemble the 146B. If you have taken more things apart, would suggest you take it to a gunsmith. There are no manuals for the 146B due to age.
It is the rifling in a mossberg rifle barrel.
There are dozens of different models of the Mossberg 22 rifle. You did not tell us which model, and we need that to give you an answer. Sorry.