Regulator Rectifier Stator

[a1steaksauce]

I own an SOHC XS400 as of today !
when wired to a new battery this thing runs beautifully but it wont charge the old battery.
Thus I figured that I would try to replace the Regulator and Rectifier (which were cheap on ebay) and then replace the stator/alternator.
However, this bike has a weird wiring system which I cannot fully understand yet
So I was wondering a couple of things:
1) Can my 1978 SOHC XS400 use the same stator as a DOHC XS400?
2) Which parts of the Stator would I need to replace? Is this sufficient? https://www.ebay.com/itm/Yamaha-197...R-MAGNETO-ROTOR-FIELD-COIL-COVER/132820605606
3) The Haynes Manual doesn't cover changing the regulator nor the rectifier and so I imagine I just plug the wires in respectively. However, can there be damage done if I put the wrong wires in the wrong places? Do you have any tips for figuring out which wires to put in where?

Thanks everyone and I know I'm asking for a quite a bit. I'm doing my own researching simultaneously and hopefully will update the thread as I go. However I would appreciate all the help!

 

[a1steaksauce]

also does anyone have any leads as to which Regulators+Rectifiers to buy? I'm afraid to buy used because I know they are often bad and was wondering which new parts I could buy instead.
To be clear my bike utilizes a separate regulator and rectifier and I would prefer not using the combo ones because I am extremely new to wiring

 

[a1steaksauce]

im planning on just buying used ones and testing their voltages to see if they'll be any good.
are the 1977 rectifiers the same as 1978 rectifiers?