Modern Vespa

First time posting on here and hoping for some advice please.

I have an 07 px200
It's been sat for a while so I decided to get it ready t for a ride.
When I started it and it got warm it has pissed gearbox oil out of the breather on the clutch cover. A little pool on the floor in less than 10 minutes.
I didn't even notice it as I was cleaning up the head light and my missus came out and told me.

I have seen some other posts on here which I have read through checking the level, was it on a side stand ect.
The oil was below the top hole when I opened it nothing came out. When I drained the oil it did have a slight fuel smell but didn't look too bad.
I took the engine out and cleaned everything up as it was pretty black back there.
I am going to put fresh oil in and give it another run.

From what I have read it's looking like it could be the clutch seal letting fuel through and causing pressure in the clutch?
I am going to try a make shit pressure test to see if it's an obvious leak.
How ever the bike starts and runs mint so would this be the case if it was leaking that bad?

My real question is, if I am replacing that should I be ordering anything else and replacing that at the same time?

Any other suggestions to what could cause this?
Any help is appreciated
Cheers. Chris

Does sound like a clutch seal leak. Especially if it's been sat around a while and if the bike is mostly stock.

Pressure test will confirm that.

Can be a can of worms opening up. Especially if you don't know the rebuild history of the engine.
Likely problems are gearbox worn gears and worn primary springs

Things to likely replace:
-Cruciform
-Kickstart o ring
-Reshim gear box (1.3mm, 1.1mm, 1.0mm most likely needed 2 of each)

3 out of 5 engines will need replacing, which you won't know until you open up the cases and pull things apart:
-Bearing change (driveshaft, main crankshaft bearing)
-oil seals
-Rebuild primary
-piston rings
-driveshaft
-gears