2) Ulka EX5. I got mine on Amazon for $26. The stock one is Ulka EP5. There are other Ulka pumps with longer duty cycles and more power. I have not tried them.

3) Any prosumer Brass OPV. I used one from a Vibiemme DD that I got from Stefanos. You will need to get the fittings for 4mm tubing, to attach the 4mm Breville tubing to the OPV. In the case of the Vibiemme OPV, it was a single 1/8" BSP-to-4mm tubing adapter. I used "quick connect" but you can use compression too. Ebay or Amazon for the fittings.

4) Breville sells the group gasket directly from their site. BUT these are extremely durable. Are you sure you need one?

5) Size #007 o-rings. If you have gone five years without them, you are on borrowed time before a leak. Either that or you have a leak already but no negative symptoms. The o-ring material is a matter of debate. My opinion (and others differ) is that you can use any material here. I used silicone because I think that's what Breville used. Don't expect more than 2-3 years between o-ring replacement. Fortunately, it's easy.

If you can get a steam ball valve (search for that thread), you probably need one of those, too. I be shocked if you don't have a little drip from your wand.

Unless you are gentle and use bare minimum torque when twisting in your portafilter, you may wear out your group collar. For your older group, those are not available (or are hard to find). If you wear out your plastic group collar insert, it's probably time to pony up the $350 repair bill, and they will address everything. Lately, people have been getting brand new machines in return. Although that's not a guarantee. Are you getting leaking around the group while under pressure? If so it's statistically more likely a worn collar than a worn group gasket.

HTH

-Peter