1. The needles will make the soil acid and could repel water so rake them up to expose the earth before scattering seed. A light covering of needles can be worked into the soil. I assume you have raised bed and improved soil so your garden does not have to compete with the tree roots. 2. Seeds can be viable for hundreds of years if kept dry but in most cases vegetable and flower seeds lose their vigor after one year but instead of wasting your old supply just plant double the amount and see if at least half of them come up. Each seed type is different so it is always a surprise to discover what seeds survive sitting around and what seeds need to be fresh for maximum germination. I usually save seed packs for just one or two years and then because seeds are inexpensive and new varieties come around I will splurge for a fresh start. Keep growing, Marianne Binetti