Gregor, usually if the trans is going to go it goes reverse first then the
other gears.  But check your fluid and linkage first before declaring it DOA.
I can get you a good price on a rebuilt autotrans with a two year warranty if
you want.  Putting a manual tranny in there and the linkage is a pretty big
undertaking and unless you have a bunch of money or your own shop I wouldn't
attempt it.
Besides the auto trans is usually way more reliable than the manual box.
Ken Wilford
'84 GL Auto
'91 Carat Auto (both runnin' strong)
'85  Vanagon manual with goofed tranny.
John 3:16