Not sure I have the time,patience or knowledge to tear down a gun. Anyone know who provides this service?

North Silva are the Diana distributors in Toronto.
Peter Krause is their gunsmith.
Tel: (416) 438-0473

Noel Sedman in Kitchener is also very good with Diana airguns.
Tel: (519) 576-1277

As far as I know, they don't do the internet, and Macarri seals and tars etc.
They rebuild to factory specs or better, with factory parts and moly and silicone lubes.

They are not inexpensive, and may be too costly if you are only looking to tinker with non-OEM springs, lubes, and tars etc.

What model is the airgun, and what are you hoping to achieve?

Thanks for the response. I bought a used Model 24. Although I don't have a chrony, it is obviously underpowered, in fact heavy pellets stick in the barrel. I just want to bring it up to factory (or better) specs. The purchase price was right so it would be worth it to spend some time or money on it.

Power so low as to leave pellets stuck in the barrel indicates a bad piston seal and/or mainspring.
If the spring is broken, you may be able to hear internal gnashing noise when you cock the gun.
If the seal is bad you can put a finger over the tranfer port and feel for suction as you CAREFULLY cock the gun.
This is not a recommend procedure without the help of a friend you trust - it's a way to lose a fingertip.
As far as I know only 500fps versions of the 24 have been brought into Canada.
If you order a new spring from the importer you will get the same low powered spring that is in the "Frei" (F in a pentagon) version Model 24.
If you have a PAL you can put a stronger spring in the gun and get 700 fps in .177 and register the gun.
The T01 trigger should easily handle the extra stress from a strong spring.
A spring with OD of approximately .85" of .118 or .122 wire would be a good piston ID (.9"+) and guide OD (.545") fit.
The non PAL 24 can be carefully disassembled without a spring compressor.
A 24 with a stronger spring would be difficult and dangerous to disassemble and/or reasemble without a compressor.
Slave pins are advised to keep the trigger and safety parts in place when reassembling Diana air rifles.
When buying used air rifles at a good price, it is always adviseable to mentally add forty dollars for new springs, seals, and parts postage, plus cost of labour.
I have a compressor, special tools and lubes, and can do the labour, and I still make regular purchases that I subsequently regret.
(NEVER another Chinese gun, NEVER)
For expensive used guns like FWB300s and Diana Giss guns, add $150 minimum for the services of Mr. Krause or Mr.Sedman.

Thanks again for your help!
This M 24 is legally registered to me (previous owner registered it as 500fps+)(so it is stored in a safe with a trigger lock) & I have a PAL, so it would be nice to get 700 fps. I have researched spring compressors and think I could make one. Or some one suggested a big wood clamp. But the trigger sounds complicated and where does one order the parts? Does Airgun Express in the US ship to Canada? Or is there a Canadian source? At this point I don't even know how to get the action out of the stock.