Bicycle Mechanics - Shimano tricolor upgrade to 10-speed

I've been looking but haven't found a specific answer in archived posts (prolly exists, but I haven't been able to find it.) I would like to upgrade my Guerc, currently running 8-speed Shimano 600 tricolor - to 10-speed. I currently have new wheels (Rol volants)
ultegra 10-speed cassette, chain and R701 STI. My LBS told me I also needed new "10-speed" chainrings and a new front derailleur. My reading is that the 10-speed chains had the same internal dimension (3/32' or something along those lines), but were made of thinner metal to allow them to slip between the thinner spacing on the cassettes.
(Also, many chainrings are sold as 9/10 speed chainrings.) So, do I really need new chainrings and a new FD, or do I need a new mechanic (laugh).

Thanks!

The old chainrings may shift OK, but 9-10 speed ones will be better due to the OD chain dimensions. You may also run into issues with the cage on the 8 speed RD being too wide to neatly manipulate the chain over the cogs.

My general rule of thumb is that Tricolor is awesome up to 8 speeds, but not so much beyond that (I've built about 20 bikes with 6400 series stuff). The crisper shift feel of components designed around 9 speeds and thinner chains is worth the price of entry, if you ask me. Even 5500/5600 105 components, which are dirt cheap these days, will outperform 6400 when you go beyond 8.

Others, of course, may disagree. Popcorn, anyone?

I've run 7s era tricolor on 9 speed and it worked all dandy, except the front derailleur needed some extra help when shifting. The rear derailleur should work fine, you may need a new front. As for chainrings, you will have to test it out. It'll work, but it won't be optimal. It depends on how fickle you are :P

Thanks for the feedback. Guess I need to save my pennies for some new chainrings.