Wish I had a friend like that...all my friends are truck drivers...lol...I also have the highlander, but used Rutlands 600 RTV and it has been doing fine so far, still haven't decided on what to use on the lids yet, but the leaks aren't that bad from them...
One thing you might consider is a fire basket. I made one from two pieces of 2-ft x 12-in Cold-RolLED Weldable Steel Expanded Sheet I got from Lowes for about $10 a piece. bent it about 6 inch from both ends then turned them 90 degree to each other and put them together to form a 12x12x6 basket. Used stainless steel small "L" brackets at each corner. Works very well and is holding up. Made keeping a fire much easier and lasting much longer since I can keep both lit and unlit coals in the basket. Of course with your friend he could probably just weld up the corners. Now I can do both coal or stick. When I do straight stick I use the grate, lump coal I use the basket.
I briefly consider buying a fire basket from GatorPits...lol...but at $155 I had a hard time justifying paying more then half of what I paid for the entire smoker. I did get a delector plate for $89 (free shipping got me) from BBQModders, mostly because I am woodworker I have no tools for working with steel, so seemed like a fair price.