I like Chambers but that kit I way over priced
the spring would be fine they are hard to hurt the breech needs and new o-ring big deal and you need a piston seal
the lubing needed is very little and I would use Ultimox 226 , you need a very little film on the inside of the tube and the backside of the piston seal and I use a little on the spring
the 5g is easier to get apart and put back together, you just need a bar clamp an a round something to put pressure on the rear piece and take out the pin
but the cocking linkage can be a problem taking apart because the pin is pressed in and the middle is knurled
you can normally tear one down in 10 mins except for that pin
I always remove some knurling at reassemble, all the early 5's had pin that pushed out easily
here are some comparison prices in euros while Chambers is in pounds
https://www.waffencenter-gotha.de/shop/index.php?manufacturers_id=2&filter_id=272 also the piston seal is a really sob to get on, you need to make a tapered dowel, something, a socket and a clamp to get seated and of course some heat to make it more pliable
cleaning the tube can be another chore if the seal has turned to crud
still message me
in any case take care
mike
I have lots of 5's, 6's and 10's
https://www.customairseals.com/product/diana-10-6-5-piston-seal/ https://www.pyramydair.com/s/a/Air_Venturi_Piston_Seal_Fits_Beeman_Diana_Models_5_6/3807 http://www.airgunspares.com/store/category/64/791/DIANA-ORIGINAL/Model%2B5%252C%2B6%2B%2526%2B10/ https://www.airrifleheadquarters.com/catalog/item/251485/7047810.htm any piston seal can be size by chucking up the piston and little sand the outside edge of the seal, easy to do on 5's impossible to do on 6's and 10's
just info rattling around in my head
remember the front piston seal is the same for the 5's, 6's, 5g, 5g mag, 6g, 6m,LP8 and model 10's and all of the Beeman, Winchester, Hy Score branded pistols