Its not if you find a good one,when my dad had his 500 we had a fantastic mobile one he could do everything a workshop could do,had a press,all merc diagnostic equipment,welder, ect all in a LWB Hiroof sprinter with trailer full rigged out as he was a support van for a rally team,but was struck down with cancer a few years ago,but i do think we were lucky to find him.
As to whats wrong look at the tech page on the Owners club and you will see the problem