1998 Honda Passport issues (multiple) please help me solve this

I have a 1998 honda passport v6 4x4. It is
my baby I hope to drive it until I total it.  It
has 192000 miles.  I just did a tune up and
had to change the leaking valve cover
gaskets.  There is another oil leak someone
from the bottom... I've checked the oil pan
and it's not that.  It almost seems like the
back of the bottom? And also our alternator
went out and when we removed it it seemed
as if oil had leaked down into the top of it
(I'm not sure if this is from a spill or
possibly when i did the valve covers) is
there anything on the passenger side
FRONT of the engine that could also
SLOWLY leak oil?   Now to the major
issues.... over the last year my
transmission went into failure mode and
pulled a code of transmission slipping I
tried to put fluid in it and it was full.  After I
reset the code it takes months for it to do it
again. I read somewhere about a possible
valve body replacement? But I'm concerned
with almost 200k it's close to the end of its
life? How difficult is it to rebuild? What
would you recommend to have it rebuilt or
buy a reman? If i bought a reman would it
be a routine swap or is there anything
different with these cars? I hope someone
can help me.  
Also what oil do you recommend? I've
consistently used havoline since I got the
car at 160k but weekday weight should I be
using?  
We just bought a radiator and I was
wanting to use honda antifreeze how do I
go about stoicism from green to blue?