In my first year of gardening, it looks like I pruned at the right time (I went round loping parts off my roses and my plum tree on Monday), well, going off the fact you've just done yours, @papa-pepper :). Some think you prune in autumn but late winter makes the most sense to me. The plant will have had all year to translocate nutrients from the branches down into the roots. When the reverse journey will shortly be happening ie. the sap begins to rise, get hacking away. At least, that's the theory I'm putting into practice.
Good work @papa-pepper. I hope you / your friends get your fruit. The plum tree in my new house had a terrible harvest last year. Hopefully, I'll have fixed all that, this year. Plums are the best but when you harvest half a dozen misshapen, insect-attacked ones from a tree you were told had had amazing harvests in the recent past, you're left with a pretty bitter taste in your mouth, aren't you!
I like late winter myself. I miss my old plum tree at our house up north, but I've got some cuttings from it grafted in down here, so I should soon taste that fruit once again.