Sorry, I missed this earlier, though I don't think I could do anything cause I don't believe you are that close, but I have to agree with Chuzie, I don't know 2.9's, but I can have access to my lifters in less then an hour (and that's through all the EFI), and unless I'm missing something it would be a matter of swapping them out, and then running your truck through a break-in to make sure there's no damage to the cam from the new lifters. Maybe I'm missing something, but honestly, removing the intake and head (if necessary, if it is inline it may be, if it's V, it shouldn't be, just losen the rocker that coinsides with the offending lifter) and swapping a couple of lifters doesn't seem like something that would amount to $800 (of course, I'd be singing a different tune if I made a living doing this stuff).
Think of it this way, atleast you'll have the peace of mind that it was done right and you have someone you can hold liable if they do anything negligently.
MoMo
Edit: Also, make sure they are not charging you for a full set of lifters unless they are replacing all of them. Go on Summitracing.com and price a set, then check that price against what they charge for parts, if it's the same, verify that they replaced them all, have them provide you with the old ones. Sometimes, they'll charge you for the full set, replace only what is needed, and keep the rest to profit twice on some other project. Just my $.02.
Think of it this way, atleast you'll have the peace of mind that it was done right and you have someone you can hold liable if they do anything negligently.
MoMo
Edit: Also, make sure they are not charging you for a full set of lifters unless they are replacing all of them. Go on Summitracing.com and price a set, then check that price against what they charge for parts, if it's the same, verify that they replaced them all, have them provide you with the old ones. Sometimes, they'll charge you for the full set, replace only what is needed, and keep the rest to profit twice on some other project. Just my $.02.