I contact manufactures with good results. I guess it depends on if they care anything about brand image. Social media means we can spread discontent with a product quickly and worldwide. One difference might be if it is an authorised dealer or not. If the OP is happy with the repair then OK, if not, then I would not just let it go.
Stihl (and other similar manufacturers) goes a long ways to protect its dealers businesses. While contacting the manufacturer may work for many products sold at retail, in this and other similar cases, you should attempt to resolve the problem with the dealer as they have far more ability to get it done than you would going to Stihl directly. Now, if you have a problem with a product and dealership management is unwilling to to go to bat for you, then taking the complaint to the OEM is quite justified. It's also much more likely to be addressed of its well documented and shows a clear unwillingness of the dealer to fulfill their responsibilities. FWIW, replacing a tank on a MS250 is a pretty big deal as its part of the chassis which the saw is built on. Would be like replacing the frame of a pickup. That said, I think Stihl would have covered the cost of the part without question plus whatever the flat-rate labor is on the repair. Somebody who has done one more than once or twice would be able to bang through it in less than an hour.
Some truth in this. I put food on my table for a few years selling/repairing OPE in an economically healthy, box-store infested area. It's true over here friend. $300 of profit on that 661 would be a damm good day. ($1200+saw). The 661 is a relatively low volume, premium product here too. Look at the smaller saws and other price sensitive equipment. The margins on that stuff hardly justifies opening the box for the customer, let alone a full prep. Which is exactly how the big stores operate. They never touch the product because it just costs too much to do so. A dealer selling a brand like Stihl has it easier because the marketing drives new sales. And you still can command full MSRP in many cases because of the high demand. Other brands are much tougher to sell, especially to the ones targeted by all that marketing. (Middle class homeowners, pro-sumers, start-up professionals, etc.). Most who are well educated about the tool they are buying are not so brand-loyal and know exactly what they want.
Great news. Now it's time to stop babying it. I predict that either it will work fine and last the lifetime of the saw or will fail rather quickly. Hopefully, the former. Either way, take off the kit gloves and run it like you want to. No sense in having a saw that you feel like you have to baby because you think it's fragile.
Not trying to stir the pot but that is a poor fix. You bought a new saw and it should be fixed right.
