thanks Jdm. I was thinking calipers and yes will probably pick up a press as suggested.
will try just to break off the rest of the glass then without mangling the case. seems like not worth the hassle to try to work out the pushers as they seem to be fairly fiddly to deal with so best avoided for me.
You don't need any special tool to remove pieces, tweezers will do. Measure size with digital calipers. But you need a press to put it back, you can get a cheap one on Ebay, just don't expect too much from them. Same for the crystal, there are specialized shops but Ebay is good for that also.
I hear it is polite to introduce yourself first so hello. I'm Irish living in Dublin. I own only a few timepieces - the most known an Omega Seamaster automatic that I bought without knowing much about watches 15 or so years ago but which I don't wear all that much anymore and may sell on. besides that I would be more into clean aesthetics than brand per se currently. Favourite watches from looks point of view would be the clean and two-tone appearance of the IWC pilots watch.