While it's a long drive from Sanur to Tulamben (3.5 hours, potentially with traffic), it's worth the trip. I was lucky enough to be the only person on the tour this time, so I traveled in a minibus, with stops along the way for restroom breaks and coffee. We arrived around noon, did one dive, and then had lunch (at the dive resort's restaurant). After a short break, we quickly did a second dive, packed up, and then took the 3-hour drive back to Sanur.
The shipwreck is huge, and two dives weren't enough to see it all. If you can stay there, you can do several dives and avoid a tiring day of driving.