Hi I need a glass for this watch. It says 2639-3 at the "back"

I've been searching around and it seems like I need a PZ5005 which is 31,6mm. Is that correct?

I live in Sweden so it seems pretty hard to get if I want to order one myself. What am I searching for if I don't find an original from Omega? I found one that is 31,6mm but apparently that's the wrong one according to another forum.

I just know those numbers, I know nothing about watch crystals.

Can I apply it with just hand pressure?

 

https://www.cousinsuk.com/product/standard-chrome-ringed-glass-atc will that work if I chose 31,6mm?

 

I think it's that one. Can I apply it by hand? Or is that stupid? I don't have a glass press.

 

If you have to ask, you can't

 

About if it's the right one or about applying it by hand?

 

Apply it. I've seen my watchmaker do it several times, and I would not try myself without training or tools