yea that would cost to replace, I would try Pipe Teflon Tape (the kind for propane and gas pipes) on the threads, that may work on getting it tight again
Yes it can. It's involved but not hard. If you want to try it I'll walk you through and if you need a reelseat I have a bunch and could send you one.
Is it a one piece rod or two.
Try the teflon tape first... it's worked for me in the past. I had to use dang near a whole roll, but it was my favorite rod and I wasn't giving it up that easy, or pay for the fix...
I also then cut strips of Gorilla tape after I got it over the part of the reel that goes in, and it's still on there right now and I fish it every weekend. That was nearly 2 years ago....