If this is a DD I would order the high pressure hose before starting this. I couldn't get the banjo bolt freed up and ended up beating the heck out of it and my hands getting it off. after reassembly the hose was leaking pretty badly. Return it if you don't need it afterwards. It's really pretty easy to redo, just go through the threads a few times and make sure you have what you need. A zip gun really makes dealing with the gear removal a breeze.
I couldn't wait and bought a remanufactured pump(don't judge me). I had the same prob with the banjo bolt so I held the high pressure port in place with a 13/16 wrench and got it loose(tip from cdan) To get the gear off I wrapped it in a terry towel doubled up 3 times and held it in a vice. I put a 17mm socket/breaker bar on the nut and smacked the breaker bar with a hammer a few times. The nut came loose and no damage to the gear. An impact would make this easy. It is in now and seems to be working fine. We will see.
Where did you buy a reman? Wish I could have helped, the Mrs has been out doing girl stuff all weekend and my boys make wrenching more difficult, bless their little hearts. Glad you got it all back together.
If you're available Tues morning I can come down and help you do the temp gauge mod.