Gundam Base Tokyo?

So my stepbrother and I are planning to go to Japan for the FIRST TIME for 2 weeks some time next year. Both massive nerds, but I'm extremely interested in going to the main Gundam Base store in Tokyo. However, hearing about how tricky it can be to actually get in has me discouraged, as it sounds like one isn't even guaranteed to be able to get in, and if you do, I hear the selection is often sold out for many popular kits. I'm worried about trying to fit it into the schedule without accidentally wasting the visit

Essentially, I need as much information I can get about how the store is run so I can plan for as good of an experience as I can. Otherwise maybe I'll just have to skip it, which would be pretty disappointing.

Thanks in advance for any advice.