Thanks, I saw that video and I'd like to try it but I have no spring compressor or space on which to give it a go. And no confidence... Anyway I appreciate the suggestions and encouragement.Seems between forums posts/ help and vids like this you should be able to do that 124 yourself. Then that experience will go a ways on doing another gun . Now with that any dissatisfaction is on you not the guy you trusted and paid good money for maybe less the expecting work .. experience is golden..
No problem , plenty of dyi ones to look at on forums , I just use a bar clamp.. cheap at harbor freight. Just make sure it's the right length one for the job/ guns ..
I changed seal on 2 Dianas both spring airgun , I bought the second one brand new from airgun of Arizona last month , first thing I did dissemble it and when I removed the piston I was shocked how dirty was inside the cylinder and the seal was damaged ,I called them for warranty but they gave me the phone number to blue line people handling warranty for Diana , I called but they never responded to my messages so I end up paying out of my pocket and got a new seal from vortex ( great people to work with ) I was getting 718 fps when I got it after I tuned it with vortex piston seal and new spring, it shoots 850 fps with 14.3 gr lead pellet , You might not need a new seal but I think personally it’s important to remove the piston and look at the condition of the seal and clean in side the cylinder very good, make it super clean , if need a new seal then you can replace it , I use moly grease only on the back of the seal not front and make sure no grease go to the the front of the seal and also you need grease to make sure when you put the piston back inside it doesn’t damage the seal , and clean the barrel then you should be good to go , for the spring compressor I found a old table and modified it for compression job
Thank you again for the thoughts and suggestions. Too much to ponder for me now. Though I will probably re-read material and watch videos. I never had heard of the 'drop-in' spring, so that's interesting too. I'll post something if I can get the time and gumption to pull this off. -dwNo problem , plenty of dyi ones to look at on forums , I just use a bar clamp.. cheap at harbor freight. Just make sure it's the right length one for the job/ guns ..
I got this one I think 36" on a sale at home Depot ( it comes with rubber pads on the clamp faces unlike the one pictured without them (??)
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Just look / google up air rifle spring compressor and should be plenty of easy homemade dyi one to review..
One thing on the spring I think make things go better is to preset the spring first.. . Not that it's nessary just makes compressing a inch easier then 4" unset raw spring ..lol ( opinion).
"Scragging tool part"
Resizing a mainspring | Blog | Pyramyd AIR
by B.B. Pelletier I recently started writing more reports about the fundamental things that many airgunners would like to know. These are things you don't have to know to shoot an air gun; but if you do know them, they can often help you recognize why your gun does what it does. You also don'twww.pyramydair.com
You can email like air rifle headquarters and request a preset spring ( use to could). And it will be pretty much a drop in spring. Maybe sand / polish the coil ends a tad , but pretty much drop right in and go .. also the vortex seals are a bit more drop in then the arh that may need sizing .
With that you got a good base rebuild. Then as you go experance wise you can start playing with different tuning set ups or power rangers , smoothness , whatever ...
Anyway don't be scared we all had our first times .... And same uncertainty.
Drop in
( the footnote on them guns tubes is kinda concerning for that priced gun)
I think.
www.airgunnation.com 
