I hate to say it, but as a guy who has made 6 tanks, it's not easy at all!
IMHO, 90% of the seal is NOT the bead that's inside the tank. It's the seam that is between the 2 pieces of glass. In fact I have made my last 2 tanks without the bead inside the tank at all.
All that said, here are a couple suggestions. You know exactly where the leak in the seal is, right? So after you do all the prep work, rather than using RTV silicone, go to Grangers (store or online) and get Teroson MS 5510 black. It's made by Loctite and it's an elastic sealant adhesive. I used it on my last build because I wanted white and I wanted to bond to both glass and acrylic at the same time. It's about $20 for a tube vs less than $10 for RTV silicone. You might even consider having a small piece of glass cut that you could bond into the inside corner of that seam (kind of assuming it at the bottom glass?).
Then protect that spot somehow so you don't bump the seal with a scraper or cleaning blade. Maybe even silicone a 'special' rock with a cool coral at that spot so you'll always know where to be careful.
The other optin is to take the entire panel of glass off the tank and reassemble it. With smaller tanks this isn't too hard. But with a 290g tank, it's a monster job that would best be reassembled by somebody with real experience (and probably a couple of helpers)!