I'm planning to submit my ERAS this week but I would like to submit my personal statement a few days later. Has anyone done this before? Is this a possibility or do i need to hand in everything at once?

your app is a 2 step process
1st step is certifying all your personal data and I believe your PS
once you certify that, submitting changes is tricky
2nd step is applying to programs and assigning PS and LOR's to programs

Yes you can do that. You can change your personal statement at any time.

I'm planning to submit my ERAS this week but I would like to submit my personal statement a few days later. Has anyone done this before? Is this a possibility or do i need to hand in everything at once?

I submitted my ERAS application (the CAF and personal data and stuff) on the first day I could (Sept 1??), but didn't finish my PS until the end of October...and it was no problem at all. I got lots of interviews w/o a PS in my file. The only reason I even got it done by the end of Oct was b/c I had a couple programs with deadlines for when my whole application had to be done, including the PS, and they wouldn't grant interviews until the app was complete. Just make sure you look at individual program requirements.
:D