Spend the mony on Brisk spark plugs. They're the only ones I've had any luck with in my 12 second DD Mustang, and I've gone through a LOT of plugs in that thing (took me a while to find the proper gap for my boost level). The Brisk plugs are a one-piece design so you never have to worry about them breaking in the head. You should get 100,000K easily running those plugs with no worries of breaking one off if you do decide to change them again. I get mine on
www.Brenspeed.com. You should have absolutely no issues pulling the stock plugs out at 35K, I would save your money and do it yourself, as it takes 30 minutes if you are mechanically inclined enough to change your own oil.