Leave this to a gunsmith
Take it to a competent gunsmith.
The Winchester model 290 belongs to the Winchester 200 series of rifles that were introduced between 1963-1965.The model 290 was discontinued in 1976.
Use a punch and tap it across the barrel. Its a dove tail joint.
your Winchester model 290 was made as a group of models including the 250,270,255,275 and the 290.these were made from 1963-1976,with the model 290 being the last model made.
your Winchester model 290 was made between 1965-1973.
the best I can do is say that your Winchester model 290 was made between 1963-1976.
remove the buttplate screws, and the buttplate. In the large round hole in the stock is the stock bolt. That is unscrewed to remove the stock from the rifle.
your Winchester model 290 in good condition should be in the range of 200-275 dollars.
Proofhouse.com has Winchester sn tables.
Unscrew the magazine tube cap, pull the barrel off to the front, remove the forestock. If in doubt, consult the owner's manual. A replacement owners manual is available through Remington's web page.
Your Winchester model 290 ranges in price from 90-200 dollars based on overall condition.