"Wondercaps" upgrade for preamp...

Just curious...I have heard of this upgrade...and I assume it is replacing the capacitators...at any rate...what would be the degree of difficulty for this upgrade? ALso...any other simple upgrades for older preamps? Anyone recommend a a skilled tech to perform these?
WonderCap was a trademark of J. Peter Moncrieff in the '80s for the polypropylene caps that Reliable Capacitor made for him. It's a term he no longer uses. His current caps are TRT DynamiCaps. I buy them from Michael Percy...http://www.percyaudio.com/Catalog.pdf . Percy has lots of fine stuff including Rel's succesors to the WonderCaps, the MultiCaps and AudioCaps.

Replacing passive parts including caps has been discussed in hundreds of threads here. SEARCH, Mr. Phase..., SEARCH. You'll learn a lot. :-)