Go buy starting strength, it's $10
For one thing you don't arch your back, you push your hips out. Use hip drive to get the bar up and lock out.
Since you don't have a "shoulder day" where you are beating the shit out of yourself for no gains or progress, you don't have to worry about injuries. Just form.
Squat shouldn't affect performance on any upper body lift unless you're killing yourself with them or (again) have poor form. Always start with squats, it's the most important lift and should be done with the most effort you can muster up.
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