The shop I was at wouldn't do customer provided parts at all because they couldn't warranty them. Not sure $1700 is a great price, but I wouldn't call it unreasonable either. Maybe check a couple of other reputable shops for over-the-phone quotes to compare.

I hear you on chronic back problems. Had back surgery a couple of years ago for a major herniation (3cm). Microdiskectomy helped immensely, like 85-90% pain reduction. Good luck with whatever yours is, back pain affects everything.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)