Removing and replacing the cam on a 103 engine does not require removing the cylinderhead.
It is instructed very thoroughly in the M/B Engine Service Manual.
If you anticipate renewing the Timing Chain at this time, a chain splitter is required. These can be rented from M/B parts suppliers.
If your cam is reground the heat treated surfaces would be removed and both the cam and followers would wear very rapidly if the cam were not re heat treated and this would require a very complex process.
Your cam is either case hardened or nitrided.
To go in depth as to the processes involved in the manufacturing would be 1 BIG BOOK.
There are after market performance cams available and they don't come cheap, how about $5-600.00. and cam manufacturers will not warrantee the came without new camfollows(lifter)12 req'd, 24 for 4 valve engines.
The costs just keep climbing and for a driver the end results may not give you what you want.
The cam may require improved exhaust.
I think you can see where we are leading.
Happy Trails Beep Beep from Houston!!!
Don, El Cheapo