Whats the best way to replace...

[Qingdao]

Inner or outer boots split?

You can replace the outer boots but the bearings inside are kind of a sealed thing. The inner bearings can be re-built, and its super easy to rebuild the inners.

Both of the boots are available online, not cheap, but available. Its about $200-$300 to get boots for all 4 joints and inner bearings. If your outer boots haven't split its the best option to do it yourself.