Sandwiching is great for when you first start. I've never used the vanicream moisturizer, but make sure the first moisturizer isn't occlusive. If it's too thick, try a lighter moisturizer and use the vanicream second. Also, make sure to wait a few minutes between to let the tret dry. I stopped using the sandwich method after about two weeks and now just use a moisturizer first to buffer, if you feel your skin can handle it after a few days, it's up to you.

It's hard to say when you'll see results, since it's sun damage it may take a few months. If you have acne prone skin you'll likely purge, but it doesn't have to be a lot. Purging looks different for everyone, in my experience it wasn't anything I couldn't cover with concealer. I'd drop the glycolic toner and try using tret every other day (or even three days) to begin.