Rear Window 90 Accord

My rear window started leaking water into the trunk. I was able to do a temp fix using RTV. How difficult is it to replace the rear window seal.

I have no idea about how hard it would be to replace the seal, my dad took my moms 91EX to a shop to do it and it got done for like $100. Apparently they had to take the rear window out and then re seal it, and put that shit back in. It had been leaking for hella long and after trying everything we could think of, my dad finally got pissed off and took it to the shop to get it done right