The trigger depends. Is there a wire on the side of the housing? If so, you could try to lighten the pull by using a smaller diameter piece of music wire. There may also be screws to adjust sear and safetty engagement. You can find more details if you search for 3-screw trigger adjustment. But there are a number of aftermarket triggers available to suit your needs. Just depends if it will be a hunting or target/varmint rifle.

The "plates" are called bases. You'll have better luck searching "scope bases" if you're looking for replacements. They should be fine as-is but I prefer to have bases that will mount the rings directly above the action instead of hanging into the loading/ejection port. You can also get a one piece base if your scope tube won't allow you mount 2-piece bases with proper eye relief.

If you unmount the scope and remount it, you'll most likely need to rezero the rifle.

As far as recoil goes, reduced loads will have a lower point of impact due to decreased velocity. A slip on recoil pad will help but tou still might have excessive muzzle rise due to the 30-06s power.

If this will be a target rifle and you dont mind some extra weight tou could opt for a varmint or bull contour barrel with the help of a few tools and a new stock. Rebarreling will also allow you to switch calibers if you want. Since you have a long action, your caliber options are almost limitless.

Feel free to pm me if you have other questions. Otherwise I'm sure others will chime in with more info.

Nice find by the way. Ive been looking for a 30-06 with iron sights. It's a very classic look.