So congrats on purchase of of W202 and welcome to the club :). Glad you liking it so far and i hope you do in future as well.
INH's work was good but now they aren't that good both in work and bucks.
First things to change:
I have been using Mobil1 from day one and is VERY satisfied with it. W202 is powered by 1.8L M111 engine and requires 6 Litres of Oil.
I am using after market Oil filters and with them, i am changing Oil at 12,000 Miles intervals. Still good to run for further 4,000 - 6,000 Miles. Mobil1 4 Litres box is for 4,950/- (Filter House & Mobil1 outlet). You can either use Mobil1 ot Liqui Moly is good as well. No need to go to INH. Buy the Oil and any Oil change guy will do the job.
Before importing after market Oil Filters, i was using MANN Oil Filters in my W202. Easily available @ YadGar, Main Boulevard, DHA or Walton Road and last time i bought was for 850/- like an Year back. Change at every Oil change. Easy job and no need to go to INH.
Using MANN Oil filters and will advice you to do the same. Costs 2,500 - 2,800. Easily available. Easy job and can be changed at home.
Cabin AC Filter.
If you feel that your AC's throw isn't that much, change the Cabin AC Filter place at front of Passenger seat below Dashboard. Cost around about 2,500/-.
ATF (Automatic Transmission Fluid) Oil.
I changed my W202's ATF at around 50,000kms. Almost 6 Litres of Oil was used and was for around 1,750/- Per Litre. Did the job at home but i will advice you to get changed from some Workshop. OEM Mercedes Recommended OIL was used.
Power Steering Fluid.
I recently changed my W202's Power Steering Fluid. OEM Mercedes Oil was used and was for 450/- Per Bottle. 2x Bottles were used.
Do check underneath if you find any broken Bushes or Control Arm. Parts isn't that expensive of W202. About workshops, Haroon bhai can tell you better as i don't know alot about workshops.