What kind of work was the tech doing -- adding/removing disk controllers? I would give him a call to discuss what happened recently that caused that unexpected change, and to express your concerns and get some clarification about the changes. Regardless, in terms of "impact", if I were in your shoes the two main concerns I'd have would be with your boot manager and your fstab. Although I obviously have no idea what kinds of scripts your organization might be using, normally you would not include specific device names; you'd simply be using directory names.
In any case, your boot manager (eg, lilo.conf or GRUB) will contain references to specific device names, as will your fstab file, and if the device names are changed that could have a negative impact if/when you are rebooting. To illustrate using a very basic example, suppose you originally had two drives in your machine, with the primary master (/dev/hda) containing the Linux system files and the primary slave (/dev/hdb) allocated to be a separate /home partition. In your fstab, there would be a line similar to
/dev/hdb1 /home ... ... ...
However, if you were to move that drive to another position, say the secondary slave (/dev/hdd) and didn't update fstab, then obviously the physical configuration of your drives would be out of sync with the specs in fstab. Along those lines, if you were to add a third drive into the primary slave position (/dev/hdb) then whatever data existed in /dev/hdb1 would be mounted to /home, which would be undesirable.
Overall you might want to just run a simple
(Note that's a lowercase "L") and compare it to the contents of your boot manager and fstab. As long as everything's in sync it should be OK. I'd really get in touch with that technician though to find out what kinds of changes he was making. Good luck with it