leaks!

Among the many challenges I have set myself for maintenance and improvement of this boat (a list with 60 items on it.. I kid you not!)... one of the highest priorities is to identify and cure any leaks..... now she not a desperately wet boat, but she does have a little water in the bilges..... When we brought her round from the Hamble it raine pretty hard one day, and there was noticeable water coming through from where the mast passes through the coachroof (keel stepped mast).... when I looked through the pile of receipts and instructions I inherited with her, there was a leaflet on the seal used.... looks pretty straightforward, but thats my first challenge to seal.... its obviously related to the gator on the deck, but also possibly a little silicon sealant will help.... The other obvious leak might be a bit tougher..... under the engine in the section of area of the bilge is a puddle... its a bit oliy... so its being supplemented with a slight oil leak from the engine (pretty minor)..... but the water is either coming from the engine/pipework (direct cooled) which may be fixeable, or from the stern gland..... its a DSS stern gland.. My plan is to dry this area out at the weekend, and then look v carefully for where it is coming from....... hope its an obvious drip from a pipe! Whatever, its not too serious.... perhaps 3 pints of water in 4 weeks, with 200M and 30hrs of motoring.... There is also a very small drip from the port side cabin window.... these windows are perspex and permanently fitted... no nice chrome surround...... the port side one has a little sealant already added, so its clearly not a new problem!.... I'll perhaps remove them over the summer (8 screws) and reseat them... but in the longer term I'm contemplating replacing them with a decent set of portholes... it'll make the boat look considerably better, and add to the resale value no end I suspect....