If there is reason to replace all of these hoses, go for it. However, you won't need the "O" ring gasket for the thermostat. The thermostat that Groton sells comes with one, and in my opinion, it's much better than the one you buy by itself. I bought the thermostat and extra "O" ring gasket from them by accident a few months ago not knowing that the thermostat came with one. I was not impressed with the quality of the one bought on its own. Buy the 87degree thermostat instead of the 90degree one. It will warm your car up and you will feel more heat in the cabin then the higher degee one and there are no adverse effects to using it in the summer either. Just my $.02

There are no replaceable part in your transmission that I know of without tearing it apart. Just flush your fluid like explained in Bay13 with a machine or on your own as IPD explains on their site (http://www.ipdusa.com/pdf/PI-290TrannyFlushKit.pdf). If you really want to upgrade your transmission lines you could put in the magnafine filters that IPD sells (http://www.ipdusa.com/ProductsCat.aspx?CategoryID=386&NodeID=277&RootID=629) ...magnetic parts pick up any loose microscopic metalic particles, but I've never done it and don't feel it's really necessary.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.