G'day and congrats
on acquiring your 154. As Bob mentioned there is only a little bit on the 154 on the server but there is a service manual of sorts, and owners manual and a parts manual. The Woods section will have the manual for your mower if it is indeed a Woods. I think it should be a right hand side discharge but you have to check the manuals to be sure.
Hydraulic Fluid - as Boss said, Hy-Tran is the best for the tranny. That said however, you can use any hydraulic fluid provided it meets or exceeds MSO 1209.
Probably the Champion D-21 will be the best plug to use especially for one that is used a lot and in all seasons. That is what I use in my F-Cubs. D-16's are a little cool to my mind - Cub can get cantankerous with the D-16's.
Hopefully this helps. Oh yeah --