Chances are its been done already but If its a Ph1 172 and you haven't had the belt changed yet, its only about 45 minutes extra job if the belts are all off, locking tools are in.
If its leaking around a bolt head - a lot of people try taking each bolt out (not all at the same time) and covering it in sealant and then going round and re-torque the bolts one by one as you put them back in.
I remeber changing on on my old fezzy. £4 for a cork gasket and a ten minutes to swap it. Those were the days lol
Haha I changed my mates 1.4 RT one the other day, 6 10mm bolts, off, wipe round with a rap, on, bolted down done!