Omega seamaster 300m 25418000 newbie questions

First thing - get the back opened and remove the battery or replace it. Batteries can leak when they are dead and corrode the movement, ruining it. If you have the correct tools and know what you are doing, this is easy to do yourself, otherwise any watchmaker can do it. The important point is to do it immediately. Don’t know how long it has been sitting in the drawer with a dead battery, but if it is more than 2-3 years, good luck. You might have a watch that is only good for parts. There’s a reason most quartz movements have an end-of-life indicator on them - so you know when to change the battery before it goes dead and can start to leak.

I had a nice watch ruined about 20 years ago because I didn’t know this and let it sit with a dead battery for a couple of years.

If the movement IS good and you really want to get the newer model and “trade” this one toward that, your best option is to: 1) replace the battery and 2) sell it privately (either locally or on EBay). A dealer will give you only a fraction of it’s worth in a trade. Then use the money you get toward the new one.

Good luck.