While this is primarily a cyborg form, there is indeed a body mod thread:
I can answer for small RFID subdermals, large anesthetic silicone implants will probably be different.
The initial puncture is what hurts the most, then it just feels weird having someone manipulate something under your skin.
When it comes to the recovery process, it depends on the size of the implants and if sutures are needed. For a small X series transponder you can get back to your life within an hour or so as long as you’re careful and keep the wound clean while it heals. Larger implants require more care and potentially more time so I’d ask someone who has a large silicone implant in the dorsal side of their hand.
These things usually take a few weeks to fully heal so you have to be careful during that time.
Also, @Coma might have something to add to this post.