It would be odd if your current Hella setup didn't have a relay (though I've seen some odd things done on my truck by PO). Easy enough to use the existing relay and rewire it.
*One hot wire (ignition) to switch
*One wire from switch to relay
*Constant hot to relay
*Ground to relay
*Wire from relay to lights (typically blue on Hella)
*Other wire from lights to ground (typically brown on Hella)
Plenty of wiring diagrams if you google it.
Remove all old wires and start fresh - use minimum 12 gauge for wires going to the lights - 18 gauge fine for others. And make sure there's a fuse on the hot lead.
All above can easily be handled by a mechanic but it's just as easy for a guy in his driveway to do with a little know how and some inspiration. Probably some local guys on the board who wouldn't mind lending a hand/knowledge.
Trickiest part is keeping wires neat and making sure all connections are good (I solder, some swear by connectors). And finding dry location for the relay.
If you take proper precautions - remove ground from battery when you start and put a fuse in line - then the worst that happens if something goes wrong should only be a blown fuse.
Save the "mechanic money" for the big stuff - you'll need it