When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Mine's a bear to get in and out sometimes - I just do my best to line it up but often have to use both hands to get it back in and seated. You might try that. Just grip as close as you can to the end as it's going back in the tube.
As for your cap being OK, I would think so. Worst case is you'll blow a little oil on your engine, but it shouldn't be much, if any.
Wonder if they boogered up something at the opening into the oil pan hence the hard in and out dipstick removal.. Ussually its the o-ring from the pan to the tube that goes bad, never heard of the tube itself rusting completely out but I guess its possible..Mine just has at the top a very light surface rust but it wipes off of sorts.
Crawl under the truck and inspect the dipstick tube carefully. It doesn't take much of a tweak to make the dipstick hard to insert. My guess is that when they worked on the oil leak (Oil Cooler?) they jacked up the engine for access and in the process bent the dipstick tube.
I had the same problem. Push the top of the dipsick tube toward the firewall, just a little bit and try again. If it is still tough to get in push a little more. After I got it pushed back to it's original position the dipstick now glides in and out easily. I must have bent the brackey while working under the hood.
EDIT : You can also loosen up the 13mm nut that holds the dipstick tube bracket and reposition it while trying to push in the dipstick.