So this is my bicycle

Good morning community. This is my first post here.

So this is my bicycle, from year about 2004 or something down there. I would like to make some improvement but it might be too pricey. I would like to put a more modern transmission: now it has a triple chainset 22, 32, 42 - as it was common back then - and a 8-speed rear cogset 11-30. I'd fancy a more recent thing and also a rear disk brake. So it means I should change the whole transmission, put a shorter freehub suitable for the disc, put the right spokes and so on. It's not urgent, but I'm thinking about it and I'm afraid of the cost of all these things.

Apart from that I'm having a really good time and I'm fond of this bicycle.

Sorry for my roughly translated technical words