Rear Main Seal, Instrument Cluster, Vents, ???

[Leewolf]

1.Rear Main Seal, does the engine have to be removed to replace the rear seal?
2. Instrument Cluster, how do I get to the light for the oil pressure, tempurature guages? Its burned out.
3. Vents, what controls the 2 vents in front of the windshield on my 79 SLC? They are mororized but I can't make them work.
4. Idle, (I didn't mention this above), I recently replaced my 450SL engine with a 450SEL engine, hot idle is so low the engine dies. I understand the Idle control is behind the glove compartment(?), if so how do I adjust it, (what does it look like ?)
Any help or thoughts would be greatly appreciated, (see my other recent post on the engine exchange)
Thanks