After 8 years of flying mine I finally broke the nose leg on a rough down hill strip where a big wind gust got me. Wasn’t a real hard landing but “snap” and the nose leg went. No where near the damage shown in your photos. I have a new nose leg from Ray which will never snap as it’s very thick compared to the old one. A new prop, the same as Kevin’s, a Bolly. Motor needed a full inspection and new flywheel and prop flange bolts. My nose wheel somehow missed the underneath of the plane so no damage there. I took off the bottom sheet behind the firewall to inspect and found some sheared rivets on the gussets. All riveted now and a new sheet installed. I moved the mains forward about 7 inches with extension pieces underneath the aircraft. This was done because mine only has a forward tank and no wing tanks and landing with full fuel and only the pilot was hard to keep the weight off the nose wheel. I have decided to replace the engine Mount rather than repair the old one as I have a Camit motor in mine and the original mount was a modified jabiru one which I was never happy with. The cowls are fixed with a bit of fibre glass and repainted. Just waiting for the engine Mount and it go back together. Good luck rebuilding your Sierra they are a great little plane and other than the nose leg issue I have had no issues at all.
The plans have the tail wheel version but the steel frame needs turning around which means a fair bit more pulling apart. I don’t know of any flying but I know at least 2 were built.