Converting (5 year) property to personal use within 5 years of claiming the section 179 subjects you to recapture: the normal dep is compared to the accelerated dep --and you pay on the excess dep that was originally taken.
Further, since vehicles fall in a special group called "listed property" the recapture rules apply any time the percentage of use for the vehicle falls below 50% for business use within in the regular recovery period. This would have been true in previous years too. And it is true even if you did not elect 179.
But from reading I take it the truck was bought 8 years ago (5 for dep and 'done for 3years now'). So if it is after the normal dep time period the basis of the property for the biz ought to be zero.
When you convert to personal property the basis transfers too. So you personally own a vehicle with zero tax basis. Whenever you sell it it will be a fully taxable sale on the full sales price. Unless you used it for biz and personal, then you have to determine your biz basis and the personal basis and figure gain appropriately for each part based on that usage ratio.
As far as procedures, just document information such as date of 'conversion', odometer, and FM Value.
If recapture applies, see IRS publication 534 & 946 at
www.irs.gov and/or your accountant to determine the actual dollar impact.