I can't find anything that indicates the amount of time involved with getting cyber implanted. Are there any?

If not, I'd be tempted to have a system that compares essence loss and gives you wound mods, which must be healed....

That's exactly how it was described in an older SR book. Cybertechnology, maybe? Or was that in Man & Machine? I don't remember.
Of course, I assume that nanotech is more popular in 2070 so if you're playing in SR4 it's probably much less than they suggest in those older books. Even then, parts like the nerve/electronic connections were created with nanites, but I imagine that more and more of the process is injected rather than inserted as time goes on. Plus, it's hard to do an abstract system when different gear will be done vastly differently.
It seems obvious to me that bone lacing must be done entirely with nanites, or else how could the patient ever survive? Conversely, a very small bit of gear like an internal air tank would definitely require cutting a hole and inserting a large tank of air.
But doesn't the fluff suggest that things like cybereyes and datajacks are trivial outpatient procedures that are performed in shopping malls?

I always figured the more essense it takes, the longer it takes to heal. The old books made healing really long.. i prefer to either let big cyber be installed at char creation or make it in the weeks and not months range. Datajack and cybereyes would be something like in and out but a couple of days of recovery.. and dont forget your morphine!

I would go along the lines with the bigger the essence dip, the longer in - say days - it takes to heal...
Maybe 1 day for every .1 essense lost... meaning stuff like cybereyes and datajacks would be day surgery, requiring a checkup after 1 week to make sure the body is accepting the implant, that there's no infection, and any fine tuning to the mods be made.

Limbs or cyberwear implants would probalby be clinic/hospital stays of about 1 week or more depending on if you want an obvious limb or a synthetic one.. synthetic cyberlimbs take time as the docs need to make sure that skin tone and hair density matches your existing metabolism... Remember, you heal faster and better under medical care, so you don't want to get out too soon.. unless you dig obvious scarring... I would probably go a far as requiring a month or so of physio training for the patient (daily or weekly visits of 1-2 hours) to get used to the proper use and balance of the implant... but that's up to the GM.