TOOLS and SPACE.
if you don't have them, and don't want to spend about $1K to get them all, then don't bother.
if you think oh the bottom end if only worth $50, I'll just give it a go, you're gonna get the shits with all the trips to bunnings and supacrap stores.
as mentioned, get the engine manual and see what tools are required, see what you have and what you need.
check the prices of what you need and see if it's worth it.
I had plans to do my own when I was in Sydney as my mechanic of many years said I could use a corner in his workshop and all his tools as I needed.
that would have been easy and if you f**ked up, you only f**ked up a $50 block.
but if you have to invest in tools, make sure you think it's worth it.