The gas side diaphragm and the air motor side diaphragm are replaceable....the oil side consists of two parts the electronics which has a rubber diaphragm that lets oil in and plugs up when the oil piston snaps towards it. The other part of the oil side is the mixing bowl it has the bore which the piston rides on and another check valve that lets oil into the mixing area and prevents gas from coming into the oil chamber(electronics part).
The oil side is available for about $86 that will include the electronics side with check valve, mixing bowl with new bore/check valve and proper sealed reset pin.
if you know how the pump works, the worry of not getting oil should be eliminated. You DO have to test the no-oil circuitry , low-oil circuitry and oil-consumption periodically. In my experience as the pump wears more oil is used, not less.
There are, however, issues with the air motor, fuel diaphragm and intermediate housing that can cause a no-fuel condition (but if there is no fuel then the motor is not running so there is no worry of not getting enough oil).
if the housing is leaking between the oil mixing bowl and intermediate housing then it is possible that the holes to which the screws insert, are worn and not squeezing the parts together and not sealing the edges properly...my fix for this condition was to fashion two crescent shape metal backings to which the screws insert..
if the gas leak is the nipples then there are o-rings that can be replaced and are available here.
if the gas leak is at the top of the reset pin, then super glue or epoxy can be applied to fix that,
I can supply pics if needed.
BUT these fixes assumes that the check valves in the intermediate housing are functional...if they are not there is no fix. you have to get a new intermediate housing, which maybe very difficult or pricey.
I just received a faulty 1990 VRO2 from a guy who had his engine just not pump fuel...diaphragms were fine...this issue was the check valves allowing the vacuum to be drawn from both the front and back of the air motor, thus a non-functioning air pump...no air pump, then no fuel...
OP your 1998 VRO is actually an OMS and is pretty good....from where is the fuel leaking? can you supply a pic?
personally I think the people selling the lawn mower style fuel pumps are gouging people (as well as bombardier with the price of a new OMS). There is no way those pumps should be $200....Not sure if there is even a source for replacement diaphragms and check valves for them.
