Mercedes: mercedes ml350 2003, mercedes ml350, auto repair business

Question
my remote on my key would not open the door (maybe it needs a new battery)so I put the key in the door and when i opened the door the alarm went off, I put the key in the ignition the alarm stop but the engine made the noise like it would start but just never turned over, I did this a few more times, then the 3rd time it started up like normal, now the check engine light is on.i am so worried, is this something that could cost me big money?

Answer
Jennifer,
I feel your pain!!!... ;-)( My 420 alarm is going haywire. Just open the door and it goes off.. will no start .. etc. etc. But that's my problem.
I would definitely change the battery in the key transmitter.
The inserted key will set off the alarm if your go the wrong direction on opening if it has been armed. It is generally reset by inserting the key in the trunk as described by the owners manual.
I would locate a copy of the owners manual and read all the details about the security system.
Sometimes, resetting the battery terminal ends will also reset the computer. With the key off, remove the battery cable terminals(negative first to avoid sparking and then the positive ), clean the post and terminal ends and reinstall in reverse order.

The check engine light is to notify you the have the vehicle checked by a service technician.
I suggest contacting the local Mercedes club to find a quality independent mechanic that specializes with Mercedes vehicles  rather than a dealer. Independent shops may be somewhat less expensive that a dealer.
This may sound sexist, but if you have a male friend or husband who is vehicle savvy and is mechanically inclined and who will deal with the mechanic, I would recommend it. Sad to say women are still taken advantage of in the auto repair business.
Remember that the least amount the dealer makes is the vehicle sales price. The back end shop is where the profit centers is. If that is possible in today's economy.
Do not just ask to have the vehicle repaired without first getting a detailed estimate including labor rates and parts prices.
The mechanic will hookup a diagnostic device that should emit numerical codes if there is a problem. There will be a flat charge to hookup the device; generally less that $100.00.
Good luck and let us know what you decide.
Rob