Tell me more about S4RS indicators

Just picking up on old threads to work out how to replace all the indicators with LEDs in my S4RS. I'm pretty confused by posts covering replacement relays, multiple & single resistors in series or parallel wired across the bulbs individually, or across the flasher unit (YIKES!) Can anyone tell me if my S4RS doesn't then have a replaceable relay (it doesn't, right?), where's best to fit what size resistor(s)? Is there an accessible common return just to fit one resistor? (NB. I don't know if this complicates things, but my alarm flashes indicators together also.)