1. Before you rebuild the transmission try to drain all of the ATF including the torque converter & changed the filter. Total cost of this is around $50. Make sure you use the right ATF when you refill the transmission. I did that to mine and it bought me about another 6 months. For a few lucky others, it corrected their problem (plugged transmission filter).
If that doesn't work, then you'll have no choice but to get the transmission rebuilt. $1800 is not that bad (about the same amount I paid for mine) just make sure they use OEM parts.
2. Get the valve job if your car needs it. "if it isn't broken, don't fix it" that has always been my motto. Preventative maintenance repairs excluded.
Good luck.
jrmd01@yahoo.com