You just have to follow your gut and experience in knowing your spouse/ex if they are genuine. In the case of my (x)W, certain body language and inability to look me in the eye when speaking is a 100% indicator on the b/s meter.
Trust issues will come and come, nature of the beast, but after all the lies and re-writing history they've done, they need to be understanding of that in advance.
Also changes. Your changes that made you the attractive "option" to want to come back, needs to be matched by changes in them to show they "deserve" to have that opportunity.
Lastly in my case, I didn't ask for much, (x)W knew what she needed to do as I carried on the notion and still do that I am now the WAS and should she faulter, life will surely go on without her (even tho I love her dearly)
That said, it's not easy, but it's not hard either. There WILL be bumps in the road. However, if you haven't forgiven, yourself and him, and subsequently accept, it's not going to work in my opinion and experience thus far. But if you have, it's worth it!
Me 35/XW 33 S13 & S12 M: 10/17/98 OM & S: 07/08 D final 06/09/09 12/03/09 - 06/13/10 "Piercing" 06/13/10: Engaged to Re-marry 10/17/10 06/25/10: Expecting baby #3 2/14/11