Hey Nitro91
Tulamben is one of the least 'touristy' spots in Bali. My partner and I actually moved to Bali last March and I knew of the USAT Liberty (one of my bucket-list dives!) before I knew it was in Tulamben
It's THE reason to make Tulamben one of your diving destinations when in Bali. So since we started diving around the area, we've based ourselves at Bali Dream Divers and assist in their marketing and dive centre management. There are several other dive spots (another large wreck that starts at 18m depth in Kubu village, 5 minutes from Tulamben); and Amed has diving too and is only marginally more 'touristy' than Tulamben (but still quiet!), is 20 minutes away and with more options for places to stay and eat.
Tulamben has 3 ATMs (not banks), about 10 restaurants (from super-cheap Balinese food-stalls, to reasonable-priced restaurants with local and western cuisine). Places to stay can range from anything between big resorts on the beach to dormitory backpacker options, but it's not all 'on-top-of-each-other' like it is in Seminyak and Kuta. So, with what's available in Tulamben, it's just not developed enough for it to get 'rowdy' with crowds all day and all night anytime soon!
Bali Dream Divers are actually offering a promotional 'Group' diving package (a minimum of 4 persons). So, if you and your girlfriend meet two other travellers, your party will receive a discount on all your dives.
I've always wanted to dive Nusa Penida as well, to dive with mola-mola and manta rays. They make their migration every year around those islands (Nusa Lembongan, Nusa Penida and Nusa Ceningan), but I'm waiting for the months between May and September for this dream to come true because I hear it's the most likely time those animals migrate around those islands... but you never know with nature, right?
So, maybe we shall meet you in a month or so in Tulamben and go dive together! But always have fun with your dive travel plans and make sure the dive professional you are to dive with makes you feel safe and comfortable!