Sure, anyone can reset the indicator, and it certainly wouldn't void a warranty (my lawyer is standing by, just in case:p )
BUT you'll just be ripping yourself off and saving MB tons of money, if enough people decide to reset it. WHY? Because the maintenance is free on this car during the warranty period. If you decide that the FSS isn't "good enough" and decide to do an oil change between services, then DO NOT reset the FSS. WHY? Because then you start over again with 10,000 miles. So if you reset it, and the FSS said you have 5000 miles to the next service, it now reads 10,000, so you will so roughly 15,000 miles before your next service, instead of the intended (roughly) 10,000 miles.
With only 4400 miles on it, there shouldn't be anything else needed. On an A service, they may try selling you a tire rotation. We usually throw it in for free, but they may recommend it and want to charge for it.
Everything in the manual for FSS is included as far as scheduled maintenance. Wear items such as brakes and tires are not included, but at 4400, shouldn't be a problem this time certainly.
On the B service the rotation IS included, also the wiper blade and climate control dust filter. The brake flush is also included, it's due every 2 years, so they should be doing that (free). The coolant is also due every 3 years on this car, so probably will wait a year for that.
BTW, the "free" maintenance work (Maintenance Commitment Plan) is ONLY done at a dealer of your choice. MB will NOT reimburse you for maintenance work done elsewhere.
If you choose not to have the dealer do the work for free, it will not void your warranty if it is done elsewhere, but yes, it would be wise to keep all receipts.