Byebye SLOB, hello golden GC!

New Brunswick
I did it, I went and bought the last 6 bottles of GC that the Canadian Tire store in town had. I also bought an air filter, pcv valve and fuel filter and an oil filter at Carquest. I had a full bottle of the SLOB in the oilpan, along with whatever oil the last owner used. The oil change went surprisingly well, I spilled maybe a few drops which is highly unusual for me. How long of an OCI should I go for? I'm thinking 7500miles/12000km. That sound good, or should I go for more, or less? BTW, I discovered a fuel leak while I had the car up on ramps. Seems to be coming from around the filler neck area. Only seems to leak when the front end is up in the air, as far as I've been able to tell. Nice, and I just put 65 bucks in the tank too! Hah, oh well, it'll give me something to do this weekend while I'm changing the fuel filter.