I'd really like to help you but I have other things I need to take care of.
I'd very much like to take the job but I can't right now because I have other work to do.
1) I'd really like to help you but I have other things I need to take care of.
「お手伝いしたいのは山々なんですが、対応しなければいけない他の用事があります。」
2) I'd very much like to take the job but I can't right now because I have other work to do.
「お仕事を受けたいのは山々なんですが、他の仕事があって今は受けられません。」
I'd really like to ... but
I'd very much like to ... but
を使って「…したいのは山々なのですが」を表現することができます。
ご参考になれば幸いです!