Best left to a gunsmith
A Westernfield M72 (actually a M72C) is a Mossberg Model 472. You might try http://www.krausebooks.com/category/firearms_knives for disassembly instructions for the Mossberg 472 in the Gun Digest Sporting Rifle Assembly/Disassembly book.
I recently bought a mossberg 472 30-30 for 285.00
The western field (montgomery wards) model 72C was made by mossberg arms company.The mossberg model 472 is the same as a western field model 72C.
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 .
100-340 or so
You have not asked a question. Yes, the lever action 472 was a 30-30 rifle, similar in many ways to the Marlin 336, made in the 1970s for a few years- at least 3 different models, value, based on condition, may range from $150-$250.
Do not attempt to use other than a Mossberg bolt made for that rifle.
50-150 or so
A Mossberg 22 rifle such as the Plinkster depending on the condition is worth around $150-200.
There are no public SN records- but your rifle was made for Western Auto by Mossberg, and is their Model 472. That model was only made from 1974-1979, when it changed to Model 479.
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.