If it is the ZSpar, usspar rig these bearings are easy to replace. There were two types depending on year. Some use a pair of rods and some use individual balls. You can buy an inexpensive loading tool if you have ball bearings. Be ready to catch them! To change you just remove the two screws and slide the car off the track. Then change the bearings. Ten minute job including cleaning everything.
I am referring to the boom I can see some ball bearings inside the track area, according to the owners manual the part is the 'main clew cart' so I guess that it is referring to your second option I will need to remove the end of the boom and check
I replaced the original boom traveler with a custom made Garhauer Marine traveler. My original traveler had a 3 to 1 purchase and was only 39" long - almost useless. So I contacted Garhauer and we designed a much larger traveler that had a 6 to 1 purchase and functioned outstanding in the last Port Huron to Mackinac race; even in the 50+ knots of a storm that ripped through the race course. I looked at Harken but just the components were twice the price and I had to do the machining. This was a breeze. I sent them the old traveler for hole spacing reference and they reproduced a new traveler for around $650 plus shipping with an additional 21" of travel. We settled on the MT-UB-2 at 60" long with a windward sheeting purchase of 6 to 1. www.garhauermarine.com/travelers/travelers/traveler-mt-ub-2.html
The traveler arrived and Imounted into the exact holes already on the deck and it has functioned perfectly. I would highly suggest to dump the original traveler and upgrade to a Garhauer traveler.
Some people seem to be talking about the mainsheet traveller used for sail trimming.... The original post, I believe, is a question about the the outhaul slider associated with in-mast furling that sits in the groove on the topside of the boom and moves backwards and forwards with the furling/unfurling of the main sail?
My 2004 vintage mast/boom is not Z-Spar and the boom has just a metal slider with no bearings. I try to keep friction to a minimum with regular application of a dry lubrication (silicon) spray - Not WD40 which attracts dirt.
This year I moved the forward stopper back along the boom to around the halfway mark which not only reduced the distance the slider has to travel but also makes for a better angle of the outhaul lines, making for easier unfurling. They now pull more aft rather than down and aft. I suggest anyone with sticky in-mast tries this. You can simply tie a loop of line around the boom to prevent forward movement.