I have been out of town, not responding during that time to forum posts.
45/19 is 2.368.
36/17 is 2.118.
2.368/2.118 is 1.118, which means that the change you propose would give you almost (but not quite) one more lower gear and you your new high gear would be very close to your current 13th gear. If that ratio was 1.13, that would be one gear change.
If that is what you want, go for it.
I use a 36/16 when touring, which is 2.25, which is right in between your existing gear and proposed gear. I get frustrated on shallow downhills because i spin out, but the low gear is low enough for me.
With a 19T sprocket, you are putting less tension on the chain than you will with the 17. Thus your sprocket wear and chain wear might be slightly greater with the new gearing. If you kept your 19T sprocket, you could go with a 40T chainring (as was mentioned before) and that would give you slightly less chain and sprocket wear than switching to a 17T.