I am actually in the process of getting a harness for myself to use with my boyfriend. It was originally his idea and I'm very receptive to it. Make sure you talk to her and she understands why you want to do this.
I'd make sure you also have at least experimented with anal as I'm told actually using a harness and having you "receive" is a bit more intense than a simple plug or probe. And make sure to use lots of lubricant!
We're looking into getting a harness by outlaw, simply because you can have a dildo on the outside and the inside (so your wife has some fun too!)
We're also planning on only buying 100% silicone dildos, because you CAN sterilize them between use. We want to do this so we can switch who's using which (after sterilizing them, of course.) If there's anything else I can help with, feel free to send me a message. While I haven't used one yet, I've done my homework and talked to quite a few people who've enjoyed them.
Or you can always message my boyfriend to get his thoughts on it as a guy (Bucking Bill)