Crack in glass interior door.

[Thingsthatgo]

In one of my interior doors there is a small crack in a pane of glass around 30cm square. It's obviously pretty old as the glass isn't toughened.
I'd like to replace it myself, as we don't have much spare cash at the moment.
What sort of thickness would I need? Should I just order it from a local glass place? If I get toughened glass will it look different from the other glass in the door?
Thank you for your help

Can you add a photo? Replacing a glass panel is pretty easy and very satisfying.

This is the cracked pane. Please note - I did not paint that gloss work myself! We bought this house as a complete bargain because every inch of it was shambolic. We are slowly making it home.
I am confident that I can do the replacing myself - I will buy some extra beading because I'm sure it won't come off cleanly. I am just not sure exactly what to buy glass wise.
Maybe I should just pop it out, then I can measure it. Will modern glass match what is there, do you think?

I’d probably take a razor blade and tidy up the other panels first, just in case another gets cracked in the process.

It looks like regular glass to me. If you take the piece to a glass place they will be able to advise you better.

Matching and cutting the beading will probably be more of a challenge...