Schubert's D.347 is a charming and approachable sonata movement, characteristic of his early lyrical style. It balances melodic sweetness with moments of greater harmonic exploration.
The main technical challenge is to bring out the singing quality of the melody while keeping the accompaniment light and unobtrusive.
Allegro moderato in C major (D.347) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 5.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Allegro moderato in C major (D.347) lasts about 5 minutes.
Allegro moderato in C major (D.347) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.