Solved it. I'll leave this here in case anyone else needs a solution. This will make the citations as follows:
Case of 1 author:
LAST name, FIRST name
Case of 2 authors:
LAST name, FIRST name, and FIRST name LAST name
Case of 3 authors:
LAST name, FIRST name, FIRST name LAST name, and FIRST name LAST name
(1) I decided to try an look at the plainnat.bst file but found I didn't have one. I dunno if it as built in or something but I decided to download it from here
(2) Save this file somewhere as something different so you don't overwrite the original plainnat.bst (wherever is is) and open it.
(3) Search for this block of code:
FUNCTION {format.names}
{ 's :=
#1 'nameptr :=
s num.names$ 'numnames :=
numnames 'namesleft :=
{ namesleft #0 > }
{ s nameptr "{ff~}{vv~}{ll}{, jj}" format.name$ 't :=
nameptr #1 >
{ namesleft #1 >
{ ", " * t * }
{ numnames #2 >
{ "," * }
'skip$
if$
t "others" =
{ " et~al." * }
{ " and " * t * }
if$
}
if$
}
't
if$
nameptr #1 + 'nameptr :=
namesleft #1 - 'namesleft :=
}
while$
}
and replace it with:
FUNCTION {format.names}
{ 's :=
#1 'nameptr :=
s num.names$ 'numnames :=
numnames 'namesleft :=
{ namesleft #0 > }
{ s nameptr "{ll,~}{ff}{vv~}{, jj}" format.name$ 't :=
nameptr #1 >
{ namesleft #1 >
{ ", " * s nameptr "{ff~}{ll}{vv~}{, jj}" format.name$ * }
{ numnames #2 >
{ "," * }
'skip$
if$
t "others" =
{ " et~al." * }
{ " and " * s nameptr "{ff~}{ll}{vv~}{, jj}" format.name$ *}
if$
}
if$
}
't
if$
nameptr #1 + 'nameptr :=
namesleft #1 - 'namesleft :=
}
while$
}
(4) Replace
\bibliographystyle{plainnat}
With whatever path and file name you need to find the file (wherever you saved it)
\bibliographystyle{/Users/joedanger/Documents/my_plainnat.bst}