Brake master cylinder - been so long I’ve forgotten how

Hello gurus! Well, I jumped into the old P6 estate today for a trip to the tip - and trod in a yucky little puddle of brake/clutch fluid. It’s leaking down the brake pedal from the master cylinder. (The reservoir is about one-third down so it’s a slowish leak.) I’m sure I replaced it like, no more than 20 years ago! Hum. I’ve ordered another but I recall it wasn’t a straightforward job. Any tips? Thank you! A
Refurb kits are readily available, but I would go for a new item myself. IIRC they are 7/8" bore. If left sitting overnight after replacement without pushing the pedal it might bleed itself, given the angle and location. I recently replaced the clutch master on a Mazda3 - real PITA, master body is plastic, the pipe to the slave is threadless, Oring sealed.