Opinions & guidance needed with turntable upgrade.

I am looking for opinions on upgrading my turntable. My current system consists of the following:

Pre-amp: Rogue Audio 99 with on-board phonostage
Amp: Cary Audio CAD120-S Mkii
Speakers: Totem Mani-2
Speaker Cables: MAC CuQ

The turntable is my 43 year old direct drive Yamaha YP-D8 which has been meticulously maintained and is in perfect running and cosmetic condition now running with a Dynavector 10x5, interconnecting via the original hard wired copper leads.

Please keep in mind that at 57 years old, while some systems are showing signs of their age, my hearing is still great. With that said, here are my questions.

1) What, in your opinion, would be the amount I would have to spend today to get a turntable that would perform on a par with the Yamaha? I have been given figures that range from the $400 to $1200.

2) Not being interested in a sidestep, in your opinion what would be an amount that I would have to spend to get, without going crazy, a noticeable increase in performance level, while still using the Dynavector?

3) In that price range, what makes and models of new turntables would you recommend I research?

4) In the same price range, what makes and models of previously owned turntables would you recommend I take a look at?

5) My technician recommends that should I hold onto the Yamaha, for around $400 he will eliminate the hard wired original copper connects replacing them with Cardas interconnects. If the increase in performance would be substantial, $400 sounds like a bargain but, again in your opinion, is this being pennywise and pound foolish vs. putting that money into replacing the Yamaha?

I know that these are complex environments we play with and there will more than likely be as many opinions as there are respondents, but your opinions are valuable to me as I begin my research in the upgrade.
Thanks,
Jerry