This is a nice guide to understand how to disassemble and assemble your Nexus 5. 95% can be done with this guide.

Tip: read the comments!

My own tips are:

1) Search for instructions how to use glue or double sided adhesive tape. It's a must if you want succesfully put everything back together

2) You need to transfer the speaker protection from the inside of the glass to the new glass

3) The same needs to be done with with a white rectangle. It has something to do with your LED-light at the bottom.

Saw these tips in this YouTube video https://youtu.be/jQS618ayL5w