Putting the work under glass is a good idea where the paper is concerned, but I don't believe it is the best idea where the oil color is concerned. An oil painting technically continues to 'dry' over many YEARS. This process for an oil painting done in impasto style (very thick) could last a couple HUNDRED YEARS! It is very important that the work 'breath'. I believe the previous suggestion to varnish it & then mount it to board using archival adhesive is your best route. Then frame. No glass. Good luck.