2 - 4 horas
No problem, just wanted the mac mini as quick as possible, so fitted 2 x 240GB SSD and RAID zero'd them
Straightforward, the guide is excellent ... the only tricky bit was replacing the wi-fi antenna, took a few goes to line it up correctly.
As the title suggests, this was a pain to ship to Serbia, they more than doubled the cost with import clearance as well as taking over a week to sort it out. Thanks to iFixit for helping with that.