has anyone replaced valve lifters on C36 motor?

1. is it a difficult job? how many hours? what is the expected mechanic charge.

2. are C36 lifters same as C280?

3. rockauto carries them for 16$ but for our 24 valves that seems to add up. should i replace them all?

4. my friends is pretty good with engines (took his corrado vr6 engine apart and put it back) but are any specials instructions he should know if he decides to do it.

Thank you