They are actually quite easy to install.
Any competent shop should have no issue installing them for you. But I personally would travel to the BMW shop.
'08 M3: AA G2L3, Catless X-Pipe & Sig Series Rear. AP rods. TC Kline EDC Coil Overs. MRF Alum Sub Frame Bushings. TMS Delrin Diff'l Bushings. BFI Motor Mounts. Recaro PP. BMW Perf Steering Wheel. P3 Gauge. PS Overflow Kit. APEX ARC-8 18"x9.5"/10.5". Conti Slicks 275/35F 305/30R. Stoptech Pads/SS Lines. Cantrell Brake Ducts.