I've been holding off on opg since i bought my e70 it was already weeping at 145k miles. A treatment occasionally woth 2 bottles of at-205 and I'll lose a quart over 6 months vs. weekly.
The repair guide is 105 pages.
If the leak you describe is what i just fixed on mine i replaced the plastic oe part with aluminum and new o-ring. It was $15. You can cut the end off the hose as it's a rare case of just hose clamp.
