1)
Why does the Torah write "asher Tasig Yado" here?
1.
Oznayim la'Torah: Presumably, it is referring to the Torim and the B'nei Yonah, since the Torim are obviously more expensive than the B'nei Yonah. So the Torah is giving him the option here as well to bring whichever birds he can afford.
2)
Why does the Torah add the 'Hey' in "ve'ha'Echad le'Olah"?
1.
Oznayim la'Torah: To indicate to the owner that, since the Olah goes entirely on the Mizbe'ach, he should designate the better animal as the Olah.