I'm really sorry for your loss. 💐
I've given a eulogy, also for my dad.
I always always sit at funerals & wish the person speaking had prepared better & written out their speech. Otherwise people tend to ramble, get upset (understandably) & fail to mention key information.
Decide what you want to say - it's fine to be brief.
You could say a little about his life, childhood, career (if relevant), what mattered to him (family, hobby, sport).
You could share a story about how much he meant to you. A way he helped you. A funny shared experience.
And as it was sudden, it's fine to acknowledge that & how shocked & devastated you are.
I typed mine, spaced it out well and spoke slowly. I wanted to get it right & I was happy with it. I included some anecdotes about early life, what he was like as a father. I made sure to mention my mum & those who'd cared for him. I didn't really need my notes but it was good to have them. I wrote it with my brother & we delivered it together & my other two siblings stood beside us.
Whatever you say will be perfect - just plan it out & take your time ❤️