Keep my number handy. If you have specific questions about the machine, I may be able to help, without having to wait on a response from the forum. I retired 2 1/2 years ago, so I am around most of the time.
Keep in mind that when sewing real leather that there are special needles for leather.
There are also different needle systems for the H3 and H4. The H3 takes a 134/35 system and the H4 takes a 190R system. Everyone will have preferences for needle brands, just like Chevy and Ford cars. There are also different needle sizes. Size will largely be gaged by the diameter thread and material you are using. V69 thread could be a 140 or 150 needle, V138 could be 150 or 160 needle.
Many Pfaff parts have generic equivalents. You are likely to pay 1/3 or 1/2 for a set of presser feet off ebay vs. a real set of Pfaff feet. Hook assemblies may be another suitable generic purchase. When it comes to shafts, gears and screws, you may want to stick with Pfaff. You can check the local suppliers. There is someone in Bradenton that is selling commercial machines, just look on Craigslist/tampabay. You can also try Dunlap/Sunbrand, remember to request generic. They will tell you if there is a generic available.