DIY - took me under 30 mins to fit the Y (I'm running OE can - but my bike is reasonably recent and all the bolts came undone ok - you may have to factor that in). It's simple engineering. Can should only take a few mins too.
Tip - if you are fitting the sensor, don't bother to undo all the wiring up the bike etc - just count the number of turns you make getting it out, then twist those into the wire before you re-attach, and you're done.
Opinions vary on re-tune - do a search for the Steptoe stuff on cat plug mods. Only way to be really sure is to get it on a dyno after you have done the job. My impresson is that most people don't change any settings - just do the re-set proceedure for the motronic. Mine is fine with the standard can a Y - not sure what effect the different can would have.
