I an a novice knitter and would like to substitute a yarn. I love the pattern but the yarn required is out of my budget range. Elann has great quality and buys but I am not sure how to substitute. The pattern calls for 20sts and 25 rows to 10cm/4in square over a K1P1 pattern on 5mm/(US 8) needles. The pattern yarn is 23 50g/1 and3/4 oz. balls of Debbie Bliss Alpaca Silk Aran. I am thinking a medium weight yarn but do I need to stick to wool? Thanks!