Suggestions on who could update and or repair a 1975 Kenwood KR 2600 receiver...

It still works and my typing mistake it is the KR 3600 

I'll restate my position given this new data, it's a 22-wpc 70s receiver. If it is working use it and enjoy it. It will cost a lot of money to have a technician go through it and even if it's 100% back to new, it's not a great piece of kit. I understand you are attached to it. Put it on a shelf, plug it in, have it light up and bask in the glory of your past. But you'll be happier if you buy an already refurbished near top of the line receiver (you know the one you really wanted but couldn't afford). A 50-year-old piece of electronics can fail an unreplaceable component at any time and make the unit unusable. I'm not trying to be mean, just trying to save you effort, time, and possible dissatisfaction. Keep us posted on your journey.  

$72. usd, works, you have the missing knobs.

you could confirm things with seller, make offer, get one going yourself, or take both units to audio classics so they would have spare parts from one to the other!

note: same seller, 110 CAD, that listing mentions ’needs some lights’. same unit?

this one is missing the wood side covers

It probably just needs some electrolytic capacitors changed. Depending on how many are replaced and what grade is used, the parts could be around $75 to $100. I work on older equipment a lot, best wishes.

I can.

Happy Listening.

@garebear 

In NY, Audio Classics, but they really focus on McIntosh. I'll give you another suggestion- in Orange County, NY- Hudson Valley Hifi. They love working on vintage gear. They have done work for me on ancient McIntosh and Marantz gear- stuff older than your Kenwood. I've been very satisfied.