If you have a spare microSD card, download & write piaware sd card image 5.0 on it. Slip out existing microsd card, slip in the spare microsd card and power up.
If you face any problems with 5.0 image on spare microsd card, you can always revert to your old microsd card.
How to Install and Configure Piaware 5.0 SD card image - Quickstart Guide
EDIT: If you are feeding other sites also, see this post also:
Re-imaging Made Easy