I retrofitted the RLS system on my E46 and it is really easy. The RLS only needs 4 wires but you will need a new windshield, RLS with mirror cover, the switch you already acquired, make a 7 ft 4 wire harness and code the car for RLS.
RLS pin 1 (KLR power)...to/from... Fuse 15 (mine was empty) (violet)
RLS pin 2 (ground)...to/from... empty connection on ground strip module above fuse box (brown)
RLS pin 3 (k-bus)...to/from... empty connection on K Bus strip module above fuse box (white/red/yellow)
RLS pin 4 (wiper motor signal)...to/from... X253 GM5 pin 45 (brown/green)
Here is the link to my E46 retrofit.
https://www.e46fanatics.com/threads/...parts.1120679/