Yes, 50/50 for the two resistors if converting down from 5V to 2.5V. For the diode, any "small signal" diode will work. I have no specific recommendation -- myself, I'll just grab whatever I can find in my parts bins, or rob one from an old motherboard or whatever.

The kind that are commonly spec'd for use with Arduino relay controllers would be fine -- you might already have some of those.

Cheers