Noob not knowing how to start after wife passed

Hi, I'm an older (30ish) player and late girlfriend used to play lots of WOW while she was going through chemo. Recently she passed away and want to get into a game that I never tried with her - I regret that. I am totally overwhelmed right now though, I've only ever played FPS. I watched a streamer video and decided instances looked like a lot of fun, can a noob do that? I haven't made an account yet because I know an expansion is coming out, should I join now or then? I want to play but I feel like I'll drag the others around me down because I don't know what I'm doing. Any tips on how to not blow? I've looked on on google but a lot of the videos seem too complex for what I'm trying to do - just start.I'd appreciate any advice, thank you.