I have a Seiko diver, that's about 16 years old and runs a little fast.  Could use cleaning and lube as well i'm sure.  Where is a reputable place to send it to?  Checking online, I see alot of places that have poor reviews.
TIA

I sent mine direct to Seiko service

https://seikousa.com/pages/support

...Seiko? Or a local AD certified for service.

Services are pricey, depending on the movement it may run ~$275. A lot of the time it's cheaper to put a new movement in than to service it. If you can find a well reviewed local independent watch place you may be able to save some money.

Years ago I learned that servicing my Seiko dive watch would cost more than I paid for the watch.  Later I just stayed with Casio and Timex.

I have two identical skx watches, I recently had both serviced. Yes, it cost as much to service them both through Seiko as what I paid for them but, they are sturdy watches. One of them I'd had for 10 years without servicing it, I only considered it when it started to drastically lose time. The other is a used watch I picked on eBay for less than I paid NIB for the other one. I had it cleaned and serviced when I got it. That particular model is no longer made and generally, NIB are going for twice or more than I paid for the one I bought in 2011.

What I have are two sturdy watches that keep good time, will most likely last for decades, and that I can leave to my SILs or grandsons if I'm lucky enough to have grandsons. I think I paid $160-70 for cleaning and overhauls per watch. The older of the two I bought a new crystal for, that was maybe $25-30. Ten years? I figure the watch I've had cost me what, 16-17 bucks a year to own.

In Tennessee I had a reputable Jeweler/Watch Smith Service my Automatics Seikos. Since I moved I found a clock smith in Indiana who is good with watches to regulate my newest watch. He nailed it, it's gained 90 seconds since I set it and changed the date July 1st. That's less than 3seconds a day.

With watches,
You have to make a basic decision.

Are you going to buy a new Dodge Neon, Toyota Corolla, or G-Wagon every ten years, and go through six cars?
Or are you going to spend as much or more keeping your ‘69 Dodge Charger, ‘70 Land Cruiser, etc. maintained and driving for decades, then it end ups with your son and maybe even grandson.

Now, if the watch is the equivalent of a Land Cruiser or G-Wagon, etc. you may feel the expense is worth it.
Is it worth it for a 4Runner?
A RAV4?