Condensing unit replacement / retrofit

Hi

im in the process of planning to retrofit a r22 system to r404a, I am replacing the old mineral oil condensing unit to a new one which will have Poe oil, the old compressor is a prestcold pl30x.
my concerns are that I have to flush the system, change drier tev etc.
which flushing agent would you recommend and how to use it, how do you get it all out!
1 With an evaporator with a liquid distributor fitted ?
2 a oil trap fitted on the outlet of the evaporator ?

any help would be appreciated