Please don't get discouraged.
Like you, I am relatively new to MB. Use this forum's "search" as often as you can. I have gone through thousands of postings/threads and learned alot.
Have a manual and parts guide? If not, use the search and draw your conclusion as to printed or CD being best for the manual. Possibly both. I have ordered the CD and the OE parts numbers through e-Bay.
These folks are great and have already created a wealth of help through their experiences.
Prices? I use FastLane & PartsShop above and if I cannot find what I am looking for I search both e-Bay and salvage sites that have been provided by this forum's members.
I am loving this '87 300TD and all that goes along with owning it. Best of luck and welcome aboard.