I am just thinking about cutting up negs to fit an enlarger and shivering. I rather like the crisper looking results of condenser, rather than colour, enlargers for B&W, but you can use either and I actualy have one of each for medium format (isn't MF strictly speaking Manual Focus?): a Durst M370 and a Meoptra Colour 3. You can get a lot cheaper than that though. You don't say which size of medium format you use, but even if you are on 6 x 6 or 6 x 4.5 it is nice to have something that will go up to at least 6 x 7 and better yet 6 x 9 just in case you go bigger in future. One thing a colour enlarger will give you, which may be of use, is the ability to use filtration when making B&W prints from col negs with panchromatic papers like Panalure (that's why I have one, I don't do col printing any more). It is an old chestnut but I would advise you to get a cheap 2nd hand enlarger (so long as it is rigid) and spend your budget on the best lens you can't afford. You can upgrade the enlarger later once you understand better what you are trying to do and so where a cheapie is holding you back, but a poor lens will hamstring you from day one.
David.
p.s. You will almost certainly be able to change the lens on your 35mm enlarger. Try unscrewing it. They run on the old Leica 39mm thread and you were originally supposed to use your Leica lens on both the camera and the enlarger (it still works). You will need a longer focal length lens for medium format though.