Pike RC convert to RCT3

If they mean exchanging the RC damper cartridge with an RC3 cartridge, that is a very easy swap. If you remove the fork, fixture it in a bikestand horizontally, and carefully remove the lower leg, you may not have to add any oil to the lowers before sliding them back on, but you will want to regrease the dust seals with a good fork grease. The RockShox service manual outlining this process for Boxxer is here. The process, tools, and steps are nearly identical for Pike.

If they mean converting an RC cartridge to an RC3, well, I don't even know if that's possible. Many of the parts necessary to make the change are not sold as serviceable parts, AFAIK, so tracking down the small individual parts might be a challenge. Truthfully, you'd be much better off just swapping cartridges.

It looks like the Pike Service Manual is on the site as well and can be found here. It also contains an exploded view for both the RC and RC3 cartridges so you can see the differences. This should make it pretty clear that you will want to swap cartridges rather than converting one to the other.

swapping the damper cartridge is relatively simple-but it sounds like your LBS messed up and unless you need the fork ASAP for a race/trip they should be doing everything they can to get you the product you payed for instead of telling you how easy the fix is, especially given the price difference between the two. hope they're doing the swap for free at the very least....i know I'm straying from the original question but sometimes you gotta put your foot down.

Rock Shox and most other manufacturers (Manitou!) are really good about making a chassis that many different dampers will fit in. It just makes good financial sense given how much a fork lower mould costs. A simple free cartridge swap, compliments of your LBS, well done Sirs, should have you on the trail in no time.