The white wall paper in my room looks old and yellow. Could you please change it?
The wall paper in my apartment has turned yellowish because it's old. Can you please replace it?
1) The white wall paper in my room looks old and yellow. Could you please change it?
「部屋の白い壁紙が古くて黄色んだけど、張り替えていただけますか？」
2) The wall paper in my apartment has turned yellowish because it's old. Can you please replace it?
「アパートの壁紙が古くて黄ばんでしまっているので、張り替えてもらえますか？」
「壁紙」は wall paper
「黄ばむ」は turn yellow, turn yellowish などと言えます。
looks old and yellow で「古くて黄色っぽい」
「壁紙を張り替える」は change the wall paper や replace the wall paper と言えます。
ご参考になれば幸いです！
日本 
