50's Tub Plumbing

My house was built in 1957, and I'm in the process of a bathroom remodel. My tub has a three handle set faucet (hot, cold and a diverter). I was looking to upgrade this three handle set to a newer three handle set, but have run into issues with matching my set up to anything modern. This is kind of a bummer because I fell in love with a faucet, only to be let down.

I already have an access panel to the plumbing through a linen closet, and to make it even easier, I have all the sheetrock down, so I can get to the plumbing with no problems. How hard is it to convert my three handle style plumbing to something that would take a single handle? Something else I'm wondering about is how hard is it to change the plumbing so I could attach a more modern handle set? Are either of these something that a newbie could do, or would it be best to call in the pros?

Thanks so much for any information!
Mary