You might have better luck asking at audiokarma.org, where there are a number of vintage Yamaha enthusiasts. One of them just recently sold 2 refurbished YP-D71s (merrylander), so he might be able to help you.
I have a YP-D8 myself and think it's great. It replaced a Thorens TD-320, which I also thought was great (but wanted the speed stability of DD).
The Signet cart may not be as "mint" as the table. You might want to try picking up an Audio Technica AT-440mla, which can be had online for about $90 shipped, and see if things sound better.
If you're new to vinyl, finding someone local to help mount and align the cart, and adjust VTA, might be a good idea. But there are lots of threads, here and on audioasylum, that walk you through it.
Good luck.
I have a YP-D8 myself and think it's great. It replaced a Thorens TD-320, which I also thought was great (but wanted the speed stability of DD).
The Signet cart may not be as "mint" as the table. You might want to try picking up an Audio Technica AT-440mla, which can be had online for about $90 shipped, and see if things sound better.
If you're new to vinyl, finding someone local to help mount and align the cart, and adjust VTA, might be a good idea. But there are lots of threads, here and on audioasylum, that walk you through it.
Good luck.