Jack, you have every right to expect payment for your knowledge and time and in no way should you fell guilty. Your story is an excellent example of people asking someone to take their time to make their own life easier. It would have been to much trouble to sell you the pump but not to much trouble to ask what it might be valued at. I sell an occasional pump part and can't tell you how many times I've been asked for a picture and a price never to hear from the person again. Not even a thank you but I'm not interested. I'm sure there will be several other people on this site that will echo the same thing. Life is short and you spent a lot of time and money collecting the knowledge you have. It's priceless information you should feel free to sell!
I apologize for adding my gripe to yours.