Is this an overnight trip, or a day trip you are thinking of?
If it's a day trip then prepare for several hours in a mini bus or coach. It's about 3.5 hours from Edinburgh to Inverness, so that's 3.5 hours on the way back too. So you're talking +/- 7 hours travelling to see an expanse of water which thanks to the "sightings" of Nessie has become something of a tourist trap. It's a pleasant enough area to look at, but there are prettier lochs in Scotland.
An organised overnight trip would give you more time in the area certainly. You might get to see Culloden and Urquhart Castle as well, but I don't know who you might be thinking of travelling with and what their itinerary is. Rabbies? Timberbush? Someone else?
Expect Fort Augustus and/or Inverness to be busy if your trip is well into the tourist season.
I've seen the Nessie Exhibition at Drumnadrochit and found it expensive for what it is. You can read all you need to know about Loch Ness and the legend of Nessie on the internet.
I've taken boat trips onto the loch from Inverness (Jacobite Tours) and Fort Augustus (Cruise Loch Ness) and preferred the latter. Mainly because you are on the water straight away whereas cruises from Inverness have to go along the river first.
I don't know if this has been of any help. If you can give me some information about what trips you are considering I might be able to assist a bit more.