Wow, this is incredibly helpful and clear, and still I am freakin intimidated to do it, not having any experience working on tractors. But one must forge ahead.
OK, you have your tractor issue fixed I see, so onward with the hoe. I have conversed with the expert and he mostly agrees with the way I have you going.
He prefers a separate electric valve if you ever want a hydraulic thumb. If you get a thumb, you want hydraulic, not manual. Reminds me that I finally decided to go electric if I ever add a thumb. But that's partly because I'd have to add a section to my Husco valve and cobble up the linkage. It's your call whether to get a 6 or 7 spool valve. If only $100-150 more, I'd get the 7. You don't have to use it, but you'd have it.
Moving on, a few pointers
• Cleanliness is important; a little dirt can cause untold grief. Clean and degrease that area before opening the system. Plug or tape any open fittings to exclude dirt, water, etc.
• Label or mark any hose you remove and the port you remove it from. Crossing connections can also cause misery. I've used an engraver, marker punches, and colored wire ties. Do not rely on permanent markers; hydraulic fluid removes it.
• I think you indicated you have the WSM for the B20; is the backhoe included? Please post the hydraulic diagram in the backhoe section. Here's the L35's:
Also, I think there will be a control valve image, similar to this, please post:
You'll notice those valves and ports are labeled. This will be useful later. Print out the valve layout so you can write down the colors or markings you use as you disconnect hoses.
• Remember to take pictures as we go along. Could you post a picture of the valve similar to the first one you posted but more directly head-on?
• Looks like you have some body work to do on the pedestal; I'm not going to address that. Do you have the top?
• Budget - you should be able to buy a valve for ~$500 and I'd budget maybe $300 for other stuff, mainly hydraulic fittings on the valve. If you select a valve with the same orientation as the existing, you can reuse the hoses, at least all but maybe two. There are cheap valves out there; one of the pictures I posted above from eBay has one for <$200. But the title and the picture don't agree so there is some risk.
• Tools, etc. - You'll obviously need wrenches to fit the hose nuts and fittings, and to remove the mounting bolts and nuts. Be prepared to drill new holes for mounting and to accommodate the levers. You may want to bend the levers later to fit your taste.
If this is agreeable, post those figures and pictures and we'll proceed.
of Simple Green, ZEP, B52, Gunk engine cleaner, any degreaser
vendors. You could save some $ if you find one with the same port threads as the OEM, so you could reuse fittings. Maybe remove one and measure.