I take it you do not have the equipment, nor experience to do the barrel work on your 91/30 yourself. The cost of the stock, scope, mount, break, and labor having a gunsmith do the work will far exceed what you could buy a decent used sporting rifle for. The Mosin Nagant 91/30 is an excellent military surplus rifle as is, and a lot of fun to shoot as it was built.
If you want to do just a quick "add on" job with the stock, scope, and scout mount, you will have an OK sporter at best if that is your goal. However, the safety is not very user friendly in that application, and safety upgrades are also costly. The barrel isn't too long, and won't cause "drag" It will probably be much more accurate if you leave it alone. Also, there really isn't a need for a break. Learn to shoot it properly with it firmly to your shoulder, and you will find the recoil is not as bad as those who shoot it sloppily say it is.
Cheapshooter's rules of gun ownership #1: NEVER SELL OR TRADE ANYTHING!