Hi Steve,
Great choice on the Model 52; it's a great gun that will serve you well for decades to come. Additionally, welcome to the Diana community!!!
You asked about a solution for mounting a sling to your 52...I have a 34 Panther, 48, 54, 350 Magnum, and a 460 Magnum for my Diana collection....I use sling kits manufactured by Uncle Mikes - I believe it is Part #: 1591-2...I believe that the package mentions that it fits Winchester Model 94 and Marlin Model??, etc.....I think that the only other model of this sling swivel setup from Uncle Mike's is designed for shotguns which will obviously be way too big on the inner diameter of the 2 piece front clamp which fits around the barrel, as you will see when you look at the parts through the clear package. I get mine at WalMart for $16 and change but they can be purchased online. You can take a look here to see what the swivel mount looks like...again, it is Part#: 1591-2 which is second down from the top:
http://www.nextag.com/uncle-mikes-sling-swivels/search-html
They are REALLY easy to install and have fairly good instructions, but here are some extra thoughts based on my experience...put a 5" piece of masking tape along the bottom edge of the stock starting at the butt-end of the stock (this will help to prevent the wood from chipping when you drill the hole) - measure up from the end of the wood, not from the end of the recoil pad) about 2.75 to 3+ inches and make a marking point that you will drill at (I use a magic marker, etc.). Follow the rest of the instructions and you will be OK. The front sling mount is a 2 piece clamp that fits around the barrel of the gun at any point that you feel is good for you. This setup is intended for 1" sling straps (some well made and sturdy synthetic padded slings can be found at WalMart in the same section as the sling mounts for under $13).
As for the big screw on the back of the dovetail scope mount, don't use it as a scope stop. They CAN shear off, but what I usually see is that the screw can dig into the metal base of the scope mount (especially on 350 mags). IF you do not remove this screw altogether, you can slip a little rubber "O" ring around it (available at hardware and home centers where they sell faucet rebuild kits, etc.) and butt the scope mount into it...it absorbs some of the "shock vibrations" as it acts like a little cushion AND it will keep the scope mount from getting chewed up by the screw.
If you are new to high-end adult airguns, you may wish to take a look at Jim Maccari's website. He offers tuning parts and full kits for many airguns which are superior in quality to the OEM parts that come from the factory. These world famous parts & kits revolve around custom wound springs and guides which "smoothes" the gun out (eliminates TWANG and some of the harshness -some power increases may be realized too). His website address is
http://www.airguns.citymax.com/page/page/251327.htm - check out the Seals section and the Tune Kits section - actually, take a trip around all of the pages of his site...there is a lot to see and learn and he has some GREAT pictures in his picture galleries.
I'm sure that the folks here will be happy to help or offer sound advice if ya run into any issues with your Diana of if ya just want to learn a few new things.
Good luck with your 52 and happy shooting!!!!!!!!!
PS...my Dianas LOVE JSB .22 Diabolo Exact Jumbo 15.8g, BEEMAN .22 Crow-Magnum 18.20g, and Air Arms .22 Cal (5.51mm), 16g Domed...check out the buy 3 get 1 free deal at PyramydAir
http://www.pyramydair.com/cgi-bin/show_necessities.pl?show=NEW&Caliber=0.22&Type=0
-Curtis