Brake pump vacuum serial numbers -oil pressure light

[snailbail]

Hi all im new to this site so firstly a big hello all. My old 2005 2.0tdi workhorse recently went a bit wobbly so im after a bit of advice as its a bit of a mystery to all including rac and garage to a degree.Any input would help as i need to decide what to do .

Last week i pulled away from work down a quiet lane and the oil pressure light came on with no knocks or bangs to be heard anywhere so immediately i pulled in and turned off engine within 20meters .got out opened bonnet and there was very slight bit of smoke/steam from the left hand side of the engine bay (not the engine) and a whirring for about 30 seconds from somewhere below and it wasn't water pump circulating as engine only just started so im told never heard noise before .

left car for ten minutes and started it again and all sounded fine i then revved slightly and light went on again (oil pressure warning) car sounded fine still so i turned it off again and called RAC. Man had a look and couldn't work it out he mentioned pump and said about this unusual whirring for about 30-45 seconds and slight bit of smoke almost like it was from manifold or exhaust somewhere after turning engine off anyway he couldn't offer explanation so i got it taken back to my garage.

Garage man initially had a look and said not sure it doesnt seem like oil pressure as it all sounds fine.He then took car down road and reported that brakes pedal wasn't working properly it was hard or soft or something like that and it had all been fine before hand but i wouldn't of noticed this at the time as i stopped straight away.He has now suggested because of this that the brake vacuum pump may be gone which could be playing a part in the oil pressure light somehow ?????? is that possible he says it seems too coincidental.

Anyway the cost of a new one and fitting is more than i want really as car is older and my works car and was written off due to scratch a year ago (laughable) so i suggested a second hand one off ebay as at least i will know if it cures the oil pressure at a fraction of the cost and apparently they dont go wrong that often so a second hand one should be ok .Now after taking the brake vacuum pump off i expected after looking online to see the number 03G145209 which seems to be related to all passat TDI 2.0 that age .But mine says 03G145200 which seems hard to get hold of does anyone know if the one 03L145100 is ok to use or a upgraded model as it seems the one linked to my car ???? any help with this would be greatly received thanks