need some advice / help with a RWS 45 --

https://www.tapatalk.com/groups/thedianawerkcollective/detailed-step-by-step-48-52-54-tuning-instructions-t2878.html

I worked on a few of them, although it's been several years ago.  With all respect I don't think the post and link immediately above this post is going to help you on your project because it's about the Diana side-lever rifles.  It sounds like you're working with one of the early Diana 45 barrel cocking rifles (they made a later version of the 45, but it didn't have that pin you have going all the way through the stock).

The pin you're describing should be the one that's a friction fit all the way through the trigger block, and therefore it should be able to be removed by tapping the pin with a punch.  It's how I did them.  Try giving the pin a definite but controlled 'rap' (not a wild swing) and I think you'll find the pin will start to move out of the other side of the stock.

I think this first link is the one that starts you down the road of working on your rifle and describes how to take it apart.  The 2nd and 3rd links offer even more info.  Have a look and a read and see what you think (you reverse the processes to put it all back together and reattach the stock to the action):

http://anotherairgunblog.blogspot.com/2011/10/rws-diana-model-45-disassembly-part-1.html

http://anotherairgunblog.blogspot.com/2011/10/rws-diana-model-45-disassembly-part-2.html

http://anotherairgunblog.blogspot.com/2011/10/rws-diana-model-45-disassembly-part-3.html

HTH.

FWIW, I have learned from firearms parts, that some 'Pins' can be/are direction sensitive. 

I know, who would have guessed. My problem has been that I can not determine with my naked eye, which is the microscopically larger end than the other end. Perhaps younger/better eyes would solve that problem for me. LOL

If I were able to determine that, I would automatically know which way to drive the pin out.  Good Luck 

doug,P.