Any oil loss during evacuation? 2 questions

[ps2cho]

I backconverted to R12 on my 260E (it was converted to r134 by PO) when I replaced the evap/exp/accum and it was working great for about 6months then it stopped....

I checked pressures and they were too low, so I got a leak somewhere.

After some thinking, the only seal I did not replace during the R&R was the big rectangular seal at the compressor manifold (just forgot I guess?)
Think thats the place it will be leaking from? I'm gonna charge it, add some UV dye and see if that is the location.

----> IF it IS....I'll need to disconnect and replace seal.

1) I shouldn't need to replace R/D in this scenario if I do it quick right?
2) Since it will be in open air and completely evacuated, do I need to add oil or does evac leave oil in the system?

I'll be using a simple dual stage vac pump.

Thanks guys