You should be able to get a GnR le for a long time. Your original mb has been hit by the remakes, but prices are likely to hold steady or increase on it as Cgc stops production. If it’s a straight up trade, I’d do it in a second. If you have to add cash, I might hold off. In terms of game play, GnR is much better.
Nobody is paying 20k for a mb. If you can get 8-9k for an original mb, I’d consider that a success.