If you can change your own oil it should be no problem for you to change the transmission fluid. Just buy 4 quarts of genuine Honda transmission fluid, that is all you need (there is a crush washer under the drain bolt that should also be changed it costs about $2) . When you drain the old fluid you will get between 3 and 4 quarts to drain out depending on how the vehicle is sitting . just measure how much came out and replace it with the same amount,and then just verify the level with the transmission dipstick. The cost of a valve adjustment should be around $100-$125 and the timing belt and water pump with parts and labor would be around $700. You might get a little break by having it all done at the same time.